Corrupt profile after upgrade

Our confluence is connected to an Oracle 9 database.
After upgrading from 2.5.2 to 2.6.1 we get the following exception with every click:

Nov 15 15:13:04 Confluence WARN WIKI n/a Errant null pointer in OSUGroupManager
java.lang.NullPointerException
at com.opensymphony.user.provider.hibernate.HibernateAccessProvider.listGroupsContainingUser(HibernateAccessProvider.java:138)
at bucket.user.providers.ChainedAccessProvider.listGroupsContainingUser(ChainedAccessProvider.java:44)
at com.atlassian.user.impl.osuser.OSUGroupManager.getGroups(OSUGroupManager.java:214)
at com.atlassian.user.impl.delegation.DelegatingGroupManagerTemplate.getGroups(DelegatingGroupManagerTemplate.java:67)
at bucket.user.DefaultUserAccessor.getGroups(DefaultUserAccessor.java:448)
at sun.reflect.GeneratedMethodAccessor121.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:287)
at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:181)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:148)
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:96)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:170)
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:176)
at $Proxy19.getGroups(Unknown Source)
at com.atlassian.confluence.security.DefaultSpacePermissionManager.hasPermissionViaGroups(DefaultSpacePermissionManager.java:339)
at com.atlassian.confluence.security.DefaultSpacePermissionManager.hasPermission(DefaultSpacePermissionManager.java:98)
at com.atlassian.confluence.security.DefaultSpacePermissionManager.hasPermission(DefaultSpacePermissionManager.java:124)
at com.atlassian.confluence.security.SpacePermissionCheckDispatcherCoordinator.hasPermission(SpacePermissionCheckDispatcherCoordinator.java:35)
at sun.reflect.GeneratedMethodAccessor235.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:287)
at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:181)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:148)
at com.atlassian.spring.interceptors.SpringProfilingInterceptor.invoke(SpringProfilingInterceptor.java:20)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:170)
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:96)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:170)
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:176)
at $Proxy18.hasPermission(Unknown Source)
at com.atlassian.confluence.pages.actions.AbstractPageAction.hasAttachFilePermissions(AbstractPageAction.java:464)
at com.atlassian.confluence.plugin.descriptor.web.conditions.ShowingPageAttachmentsCondition.shouldDisplay(ShowingPageAttachmentsCondition.java:15)
at com.atlassian.confluence.plugin.descriptor.web.conditions.AbstractConfluenceCondition.shouldDisplay(AbstractConfluenceCondition.java:21)
at com.atlassian.plugin.web.DefaultWebInterfaceManager.filterFragmentsByCondition(DefaultWebInterfaceManager.java:118)
at com.atlassian.plugin.web.DefaultWebInterfaceManager.getDisplayableItems(DefaultWebInterfaceManager.java:102)
at com.atlassian.confluence.plugin.descriptor.web.ConfluenceWebInterfaceManager.getDisplayableItems(ConfluenceWebInterfaceManager.java:53)
at com.atlassian.confluence.plugin.descriptor.web.ConfluenceWebInterfaceManager.getDisplayableItems(ConfluenceWebInterfaceManager.java:58)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at org.apache.velocity.runtime.parser.node.ASTMethod.execute(ASTMethod.java:260)
at org.apache.velocity.runtime.parser.node.ASTReference.execute(ASTReference.java:207)
at org.apache.velocity.runtime.parser.node.ASTReference.value(ASTReference.java:357)
at org.apache.velocity.runtime.directive.Foreach.getIterator(Foreach.java:203)
at org.apache.velocity.runtime.directive.Foreach.render(Foreach.java:325)
at org.apache.velocity.runtime.parser.node.ASTDirective.render(ASTDirective.java:153)
at org.apache.velocity.runtime.parser.node.SimpleNode.render(SimpleNode.java:271)
at org.apache.velocity.Template.merge(Template.java:296)
at com.atlassian.confluence.util.velocity.VelocityUtils.getRenderedTemplateWithoutSwallowingErrors(VelocityUtils.java:53)
at com.atlassian.confluence.setup.velocity.ApplyDecoratorDirective.render(ApplyDecoratorDirective.java:229)
at org.apache.velocity.runtime.parser.node.ASTDirective.render(ASTDirective.java:153)
at org.apache.velocity.runtime.parser.node.SimpleNode.render(SimpleNode.java:271)
at org.apache.velocity.runtime.directive.VelocimacroProxy.render(VelocimacroProxy.java:215)
at org.apache.velocity.runtime.parser.node.ASTDirective.render(ASTDirective.java:153)
at org.apache.velocity.runtime.parser.node.ASTBlock.render(ASTBlock.java:94)
at org.apache.velocity.runtime.parser.node.ASTElseIfStatement.render(ASTElseIfStatement.java:118)
at org.apache.velocity.runtime.parser.node.ASTIfStatement.render(ASTIfStatement.java:128)
at org.apache.velocity.runtime.parser.node.SimpleNode.render(SimpleNode.java:271)
at org.apache.velocity.Template.merge(Template.java:296)
at com.atlassian.confluence.util.velocity.VelocityUtils.getRenderedTemplateWithoutSwallowingErrors(VelocityUtils.java:53)
at com.atlassian.confluence.setup.velocity.ApplyDecoratorDirective.render(ApplyDecoratorDirective.java:229)
at org.apache.velocity.runtime.parser.node.ASTDirective.render(ASTDirective.java:153)
at org.apache.velocity.runtime.parser.node.SimpleNode.render(SimpleNode.java:271)
at org.apache.velocity.Template.merge(Template.java:296)
at com.opensymphony.webwork.dispatcher.VelocityResult.doExecute(VelocityResult.java:91)
at com.atlassian.xwork.results.ProfiledVelocityResult.doExecute(ProfiledVelocityResult.java:21)
at com.opensymphony.webwork.dispatcher.WebWorkResultSupport.execute(WebWorkResultSupport.java:116)
at com.opensymphony.xwork.DefaultActionInvocation.executeResult(DefaultActionInvocation.java:263)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:187)
at com.opensymphony.xwork.interceptor.AroundInterceptor.intercept(AroundInterceptor.java:35)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:165)
at com.opensymphony.xwork.interceptor.DefaultWorkflowInterceptor.intercept(DefaultWorkflowInterceptor.java:55)
at com.atlassian.confluence.core.ConfluenceWorkflowInterceptor.intercept(ConfluenceWorkflowInterceptor.java:39)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:165)
at com.opensymphony.xwork.interceptor.AroundInterceptor.intercept(AroundInterceptor.java:35)
at com.atlassian.confluence.core.ConfluenceValidationInterceptor.intercept(ConfluenceValidationInterceptor.java:16)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:165)
at com.opensymphony.xwork.interceptor.AroundInterceptor.intercept(AroundInterceptor.java:35)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:165)
at com.atlassian.confluence.util.LoggingContextInterceptor.intercept(LoggingContextInterceptor.java:48)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:165)
at com.atlassian.confluence.security.actions.PermissionCheckInterceptor.intercept(PermissionCheckInterceptor.java:47)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:165)
at com.atlassian.confluence.pages.actions.PageAwareInterceptor.intercept(PageAwareInterceptor.java:114)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:165)
at com.atlassian.confluence.spaces.actions.SpaceAwareInterceptor.intercept(SpaceAwareInterceptor.java:67)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:165)
at com.opensymphony.xwork.interceptor.AroundInterceptor.intercept(AroundInterceptor.java:35)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:165)
at com.atlassian.confluence.core.actions.LastModifiedInterceptor.intercept(LastModifiedInterceptor.java:39)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:165)
at com.atlassian.confluence.core.ConfluenceAutowireInterceptor.intercept(ConfluenceAutowireInterceptor.java:25)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:165)
at com.opensymphony.xwork.interceptor.AroundInterceptor.intercept(AroundInterceptor.java:35)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:165)
at com.opensymphony.xwork.interceptor.AroundInterceptor.intercept(AroundInterceptor.java:35)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:165)
at com.atlassian.xwork.interceptors.XWorkTransactionInterceptor.intercept(XWorkTransactionInterceptor.java:98)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:165)
at com.opensymphony.xwork.interceptor.AroundInterceptor.intercept(AroundInterceptor.java:35)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:165)
at com.opensymphony.xwork.DefaultActionProxy.execute(DefaultActionProxy.java:115)
at com.opensymphony.webwork.dispatcher.ServletDispatcher.serviceAction(ServletDispatcher.java:229)
at com.opensymphony.webwork.dispatcher.ServletDispatcher.service(ServletDispatcher.java:199)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:252)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:672)
at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:463)
at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:398)
at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:301)
at com.atlassian.confluence.servlet.simpledisplay.SimpleDisplayServlet.doGet(SimpleDisplayServlet.java:81)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:689)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:252)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at com.logicacmg.wiki.user.TermsOfUseFilter.doFilter(TermsOfUseFilter.java:127)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at com.opensymphony.module.sitemesh.filter.PageFilter.parsePage(PageFilter.java:118)
at com.atlassian.confluence.util.profiling.ProfilingPageFilter.parsePage(ProfilingPageFilter.java:137)
at com.opensymphony.module.sitemesh.filter.PageFilter.doFilter(PageFilter.java:54)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at com.atlassian.core.filters.ServletContextThreadLocalFilter.doFilter(ServletContextThreadLocalFilter.java:21)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at com.atlassian.confluence.util.LoggingContextFilter.doFilter(LoggingContextFilter.java:46)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at com.atlassian.confluence.util.UserThreadLocalFilter.doFilter(UserThreadLocalFilter.java:44)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at com.atlassian.seraph.filter.SecurityFilter.doFilter(SecurityFilter.java:182)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at com.atlassian.seraph.filter.LoginFilter.doFilter(LoginFilter.java:161)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at com.atlassian.confluence.util.ClusterHeaderFilter.doFilter(ClusterHeaderFilter.java:35)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at com.atlassian.johnson.filters.JohnsonFilter.doFilter(JohnsonFilter.java:96)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at org.springframework.orm.hibernate.support.OpenSessionInViewFilter.doFilterInternal(OpenSessionInViewFilter.java:174)
at com.atlassian.spring.filter.FlushingSpringSessionInViewFilter.doFilterInternal(FlushingSpringSessionInViewFilter.java:29)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at com.atlassian.util.profiling.filters.ProfilingFilter.doFilter(ProfilingFilter.java:140)
at com.atlassian.core.filters.ProfilingAndErrorFilter.doFilter(ProfilingAndErrorFilter.java:27)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at com.atlassian.confluence.util.RequestCacheThreadLocalFilter.doFilter(RequestCacheThreadLocalFilter.java:25)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at com.atlassian.core.filters.gzip.GzipFilter.doFilter(GzipFilter.java:61)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at com.atlassian.core.filters.AbstractEncodingFilter.doFilter(AbstractEncodingFilter.java:37)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:178)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:126)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:105)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:107)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:148)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:869)
at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:664)
at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:527)
at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:80)
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:684)
at java.lang.Thread.run(Thread.java:595)