ConcurrentModificationException if you move two portlets on the dasboard at the same time

java.util.ConcurrentModificationException
at java.util.AbstractList$Itr.checkForComodification()V(Optimized Method)
at java.util.AbstractList$Itr.next()Ljava/lang/Object;(Optimized Method)
at java.util.Collections$1.next()Ljava/lang/Object;(Optimized Method)
at webwork.view.taglib.IteratorTag.doAfterBody()I(IteratorTag.java:119)
at jsp._secure._views._dashboardjsp._jspService(Ljavax/servlet/http/HttpServletRequest;Ljavax/servlet/http/HttpServletResponse;)V(_dashboard_jsp.java:1646)
at com.caucho.jsp.JavaPage.service(Ljavax/servlet/ServletRequest;Ljavax/servlet/ServletResponse;)V(Optimized Method)
at com.caucho.jsp.Page.pageservice(Ljavax/servlet/http/HttpServletRequest;Ljavax/servlet/http/HttpServletResponse;)V(Optimized Method)
at com.caucho.server.dispatch.PageFilterChain.doFilter(Ljavax/servlet/ServletRequest;Ljavax/servlet/ServletResponse;)V(PageFilterChain.java:159)
at com.caucho.server.webapp.DispatchFilterChain.doFilter(Ljavax/servlet/ServletRequest;Ljavax/servlet/ServletResponse;)V(DispatchFilterChain.java:115)
at com.caucho.server.dispatch.ServletInvocation.service(Ljavax/servlet/ServletRequest;Ljavax/servlet/ServletResponse;)V(ServletInvocation.java:208)
at com.caucho.server.webapp.RequestDispatcherImpl.forward(Ljavax/servlet/http/HttpServletRequest;Ljavax/servlet/http/HttpServletResponse;Ljava/lang/String;Lcom/caucho/server/dispatch/Invocation;)V(RequestDispatcherImpl.java:268)
at com.caucho.server.webapp.RequestDispatcherImpl.forward(Ljavax/servlet/ServletRequest;Ljavax/servlet/ServletResponse;)V(RequestDispatcherImpl.java:106)
at com.atlassian.jira.web.dispatcher.JiraServletDispatcher.service(Ljavax/servlet/http/HttpServletRequest;Ljavax/servlet/http/HttpServletResponse;)V(JiraServletDispatcher.java:249)
at javax.servlet.http.HttpServlet.service(Ljavax/servlet/ServletRequest;Ljavax/servlet/ServletResponse;)V(HttpServlet.java:92)
at com.caucho.server.dispatch.ServletFilterChain.doFilter(Ljavax/servlet/ServletRequest;Ljavax/servlet/ServletResponse;)V(ServletFilterChain.java:99)
at com.atlassian.jira.web.filters.AccessLogFilter.doFilter(Ljavax/servlet/ServletRequest;Ljavax/servlet/ServletResponse;Ljavax/servlet/FilterChain;)V(AccessLogFilter.java:51)
at com.caucho.server.dispatch.FilterFilterChain.doFilter(Ljavax/servlet/ServletRequest;Ljavax/servlet/ServletResponse;)V(Optimized Method)
at com.opensymphony.module.sitemesh.filter.PageFilter.parsePage(Ljavax/servlet/http/HttpServletRequest;Ljavax/servlet/http/HttpServletResponse;Ljavax/servlet/FilterChain;)Lcom/opensymphony/module/sitemesh/Page;(PageFilter.java:119)
at com.opensymphony.module.sitemesh.filter.PageFilter.doFilter(Ljavax/servlet/ServletRequest;Ljavax/servlet/ServletResponse;Ljavax/servlet/FilterChain;)V(PageFilter.java:55)
at com.atlassian.jira.web.filters.SitemeshExcludePathFilter.doFilter(Ljavax/servlet/ServletRequest;Ljavax/servlet/ServletResponse;Ljavax/servlet/FilterChain;)V(SitemeshExcludePathFilter.java:38)
at com.caucho.server.dispatch.FilterFilterChain.doFilter(Ljavax/servlet/ServletRequest;Ljavax/servlet/ServletResponse;)V(Optimized Method)
at com.atlassian.seraph.filter.SecurityFilter.doFilter(Ljavax/servlet/ServletRequest;Ljavax/servlet/ServletResponse;Ljavax/servlet/FilterChain;)V(Optimized Method)
at com.caucho.server.dispatch.FilterFilterChain.doFilter(Ljavax/servlet/ServletRequest;Ljavax/servlet/ServletResponse;)V(Optimized Method)
at com.atlassian.seraph.filter.LoginFilter.doFilter(Ljavax/servlet/ServletRequest;Ljavax/servlet/ServletResponse;Ljavax/servlet/FilterChain;)V(Optimized Method)
at com.caucho.server.dispatch.FilterFilterChain.doFilter(Ljavax/servlet/ServletRequest;Ljavax/servlet/ServletResponse;)V(Optimized Method)
at com.atlassian.util.profiling.filters.ProfilingFilter.doFilter(Ljavax/servlet/ServletRequest;Ljavax/servlet/ServletResponse;Ljavax/servlet/FilterChain;)V(ProfilingFilter.java:132)
at com.atlassian.jira.web.filters.ProfilingAndErrorFilter.doFilter(Ljavax/servlet/ServletRequest;Ljavax/servlet/ServletResponse;Ljavax/servlet/FilterChain;)V(ProfilingAndErrorFilter.java:25)
at com.caucho.server.dispatch.FilterFilterChain.doFilter(Ljavax/servlet/ServletRequest;Ljavax/servlet/ServletResponse;)V(Optimized Method)
at com.atlassian.jira.web.filters.ActionCleanupDelayFilter.doFilter(Ljavax/servlet/ServletRequest;Ljavax/servlet/ServletResponse;Ljavax/servlet/FilterChain;)V(ActionCleanupDelayFilter.java:39)
at com.caucho.server.dispatch.FilterFilterChain.doFilter(Ljavax/servlet/ServletRequest;Ljavax/servlet/ServletResponse;)V(Optimized Method)
at com.atlassian.johnson.filters.JohnsonFilter.doFilter(Ljavax/servlet/ServletRequest;Ljavax/servlet/ServletResponse;Ljavax/servlet/FilterChain;)V(JohnsonFilter.java:91)
at com.caucho.server.dispatch.FilterFilterChain.doFilter(Ljavax/servlet/ServletRequest;Ljavax/servlet/ServletResponse;)V(Optimized Method)