SearchRequest error: ClassNotFoundException with CustomFieldStringParameter after upgrade

Our log shows this error:

2006-04-05 18:06:34,137 ERROR [jira.issue.search.SearchRequest] Could not create parameter class: com.atlassian.jira.issue.search.parameters.lucene.CustomFieldStringParameter. Element: <parameter class='com.atlassian.jira.issue.search.parameters.lucene.CustomFieldStringParameter'>
<customfield_10091 name='customfield_10091' value='"Elecci?n del proyecto asociado al ticket / Datos identificativos del usuario llamante / Datos generales de la incidencia / Selecci?n del servicio afectado / Selecci?n del tipo de Base de Datos"' customfield='10091'/>
</parameter>
java.lang.ClassNotFoundException: com.atlassian.jira.issue.search.parameters.lucene.CustomFieldStringParameter
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1332)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1181)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:302)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:141)
at com.atlassian.jira.issue.search.SearchRequest.init(SearchRequest.java:206)
at com.atlassian.jira.issue.search.SearchRequest.<init>(SearchRequest.java:176)
at com.atlassian.jira.issue.search.SearchRequestManagerImpl.loadByMap(SearchRequestManagerImpl.java:265)
at com.atlassian.jira.issue.search.SearchRequestManagerImpl.getSearchRequest(SearchRequestManagerImpl.java:230)
at com.atlassian.jira.issue.search.SearchRequestManagerImpl.getRequest(SearchRequestManagerImpl.java:203)
at com.atlassian.jira.portal.portlets.SavedFiltersPortlet.getCountsForFilter(SavedFiltersPortlet.java:51)
at sun.reflect.GeneratedMethodAccessor92.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:324)
at org.apache.velocity.util.introspection.UberspectImpl$VelMethodImpl.invoke(UberspectImpl.java:267)
at org.apache.velocity.runtime.parser.node.ASTMethod.execute(ASTMethod.java:197)
at org.apache.velocity.runtime.parser.node.ASTReference.execute(ASTReference.java:175)
at org.apache.velocity.runtime.parser.node.ASTReference.render(ASTReference.java:220)
at org.apache.velocity.runtime.parser.node.ASTBlock.render(ASTBlock.java:55)
at org.apache.velocity.runtime.parser.node.ASTIfStatement.render(ASTIfStatement.java:70)
at org.apache.velocity.runtime.parser.node.ASTBlock.render(ASTBlock.java:55)
at org.apache.velocity.runtime.directive.Foreach.render(Foreach.java:166)
at org.apache.velocity.runtime.parser.node.ASTDirective.render(ASTDirective.java:114)
at org.apache.velocity.runtime.parser.node.ASTBlock.render(ASTBlock.java:55)
at org.apache.velocity.runtime.parser.node.ASTIfStatement.render(ASTIfStatement.java:70)
at org.apache.velocity.runtime.parser.node.SimpleNode.render(SimpleNode.java:230)
at org.apache.velocity.Template.merge(Template.java:256)
at org.apache.velocity.app.VelocityEngine.mergeTemplate(VelocityEngine.java:450)
at com.atlassian.velocity.DefaultVelocityManager.getEncodedBody(DefaultVelocityManager.java:76)
at com.atlassian.velocity.DefaultVelocityManager.getEncodedBody(DefaultVelocityManager.java:60)
at com.atlassian.velocity.DefaultVelocityManager.getEncodedBody(DefaultVelocityManager.java:55)
at com.atlassian.jira.plugin.JiraResourcedModuleDescriptor.getHtml(JiraResourcedModuleDescriptor.java:97)
at com.atlassian.jira.portal.PortletImpl.getViewHtml(PortletImpl.java:65)
at com.atlassian.jira.portal.portlets.AbstractRequiresUserPortlet.getViewHtml(AbstractRequiresUserPortlet.java:25)
at org.apache.jsp.secure.views.dashboard_jsp._jspService(org.apache.jsp.secure.views.dashboard_jsp:1090)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:97)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)