Our log files contains this exception quite often. I have no clue what scenario reproduces it and whether the users see an error message on screen when this happens.

Maybe it is related to javax.faces.FacesException: Cannot add the same component twice: sub:menuForm:headermenu:j_idt26:j_id10:link? Users complain about application crashes a few times per day that can be linked to this "Cannot add the same component twice" message.

SEVERE: Servlet.service() for servlet Faces Servlet threw exception
java.util.ConcurrentModificationException
at java.util.HashMap$HashIterator.nextNode(HashMap.java:1429)
at java.util.HashMap$ValueIterator.next(HashMap.java:1458)
at org.icefaces.impl.push.DynamicResourceDispatcher$SessionBasedResourceDispatcher.handleResourceRequest(DynamicResourceDispatcher.java:148)
at org.icefaces.impl.push.DynamicResourceDispatcher.handleResourceRequest(DynamicResourceDispatcher.java:76)
at org.icefaces.application.ResourceRegistry.handleResourceRequest(ResourceRegistry.java:108)
at org.icefaces.impl.application.WindowScopeManager.handleSessionAwareResourceRequest(WindowScopeManager.java:68)
at org.icefaces.impl.application.SessionAwareResourceHandlerWrapper.handleResourceRequest(SessionAwareResourceHandlerWrapper.java:40)
at javax.faces.application.ResourceHandlerWrapper.handleResourceRequest(ResourceHandlerWrapper.java:125)
at org.icefaces.impl.application.SessionTimeoutMonitor.handleSessionAwareResourceRequest(SessionTimeoutMonitor.java:71)
at org.icefaces.impl.application.SessionAwareResourceHandlerWrapper.handleResourceRequest(SessionAwareResourceHandlerWrapper.java:40)
at javax.faces.application.ResourceHandlerWrapper.handleResourceRequest(ResourceHandlerWrapper.java:125)
at javax.faces.application.ResourceHandlerWrapper.handleResourceRequest(ResourceHandlerWrapper.java:125)
at javax.faces.application.ResourceHandlerWrapper.handleResourceRequest(ResourceHandlerWrapper.java:125)
at javax.faces.application.ResourceHandlerWrapper.handleResourceRequest(ResourceHandlerWrapper.java:125)
at javax.faces.application.ResourceHandlerWrapper.handleResourceRequest(ResourceHandlerWrapper.java:125)
at javax.faces.application.ResourceHandlerWrapper.handleResourceRequest(ResourceHandlerWrapper.java:125)
at org.icefaces.impl.application.AuxUploadResourceHandler.handleResourceRequest(AuxUploadResourceHandler.java:82)
at javax.faces.webapp.FacesServlet.service(FacesServlet.java:591)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:465)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298)
at org.apache.coyote.http11.Http11AprProcessor.process(Http11AprProcessor.java:859)
at org.apache.coyote.http11.Http11AprProtocol$Http11ConnectionHandler.process(Http11AprProtocol.java:579)
at org.apache.tomcat.util.net.AprEndpoint$Worker.run(AprEndpoint.java:1555)
at java.lang.Thread.run(Thread.java:745)