After a random period of time we are starting to see random NPE they mainly seem to be from the ResourceServlet and WebEngineServlet but some user have experience in the nuxeo web ui as well. A server restart seems to make them go away but they return. If you refresh the page a couple of times the page will eventually load correctly. Look through JIRA is can see issue NXP-3607 but that relates to the DownloadServlet but maybe this issue is similar
009-05-28 16:31:24,446 ERROR [org.apache.catalina.core.ContainerBase.[jboss.web].[localhost].[/nuxeo].[Nuxeo Resource Servlet]] Servlet.service() for servlet Nuxeo Resource Servlet threw exception
java.lang.NullPointerException
at org.apache.catalina.connector.Request.removeAttribute(Request.java:1354)
at org.apache.catalina.connector.RequestFacade.removeAttribute(RequestFacade.java:514)
at org.jboss.seam.mock.MockExternalContext$2.removeAttribute(MockExternalContext.java:274)
at org.jboss.seam.mock.MockExternalContext$AttributeMap.remove(MockExternalContext.java:471)
at org.jboss.seam.contexts.BasicContext.remove(BasicContext.java:73)
at org.jboss.seam.Component.newInstance(Component.java:2070)
at org.jboss.seam.Component.getInstance(Component.java:1962)
at org.jboss.seam.Component.getInstance(Component.java:1941)
at org.jboss.seam.Component.getInstance(Component.java:1918)
at org.jboss.seam.Component.getInstance(Component.java:1913)
at org.jboss.seam.transaction.Transaction.instance(Transaction.java:36)
at org.nuxeo.ecm.webapp.shield.SeamExceptionHandlingListener.rollbackTransactionIfNecessary(SeamExceptionHandlingListener.java:101)
at org.nuxeo.ecm.webapp.shield.SeamExceptionHandlingListener.startHandling(SeamExceptionHandlingListener.java:89)
at org.nuxeo.ecm.platform.web.common.exceptionhandling.NuxeoExceptionHandler.handleException(NuxeoExceptionHandler.java:103)
at org.nuxeo.ecm.platform.web.common.exceptionhandling.NuxeoExceptionFilter.handleException(NuxeoExceptionFilter.java:55)
at org.nuxeo.ecm.platform.web.common.exceptionhandling.NuxeoExceptionFilter.doFilter(NuxeoExceptionFilter.java:64)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:96)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:230)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
at org.jboss.web.tomcat.security.SecurityAssociationValve.invoke(SecurityAssociationValve.java:182)
at org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValve.java:84)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.jboss.web.tomcat.service.jca.CachedConnectionValve.invoke(CachedConnectionValve.java:157)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:262)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:446)
at java.lang.Thread.run(Thread.java:619)
And
2009-05-28 16:31:38,783 ERROR [org.apache.catalina.core.ContainerBase.[jboss.web].[localhost].[/nuxeo].[Nuxeo WebEngine Servlet]] Servlet.service() for servlet Nuxeo WebEngine Servlet threw exception
java.lang.NullPointerException
at org.apache.catalina.connector.Request.removeAttribute(Request.java:1354)
at org.apache.catalina.connector.RequestFacade.removeAttribute(RequestFacade.java:514)
at org.jboss.seam.mock.MockExternalContext$2.removeAttribute(MockExternalContext.java:274)
at org.jboss.seam.mock.MockExternalContext$AttributeMap.remove(MockExternalContext.java:471)
at org.jboss.seam.contexts.BasicContext.remove(BasicContext.java:73)
at org.jboss.seam.Component.newInstance(Component.java:2070)
at org.jboss.seam.Component.getInstance(Component.java:1962)
at org.jboss.seam.Component.getInstance(Component.java:1941)
at org.jboss.seam.Component.getInstance(Component.java:1918)
at org.jboss.seam.Component.getInstance(Component.java:1913)
at org.jboss.seam.transaction.Transaction.instance(Transaction.java:36)
at org.nuxeo.ecm.webapp.shield.SeamExceptionHandlingListener.rollbackTransactionIfNecessary(SeamExceptionHandlingListener.java:101)
at org.nuxeo.ecm.webapp.shield.SeamExceptionHandlingListener.startHandling(SeamExceptionHandlingListener.java:89)
at org.nuxeo.ecm.platform.web.common.exceptionhandling.NuxeoExceptionHandler.handleException(NuxeoExceptionHandler.java:103)
at org.nuxeo.ecm.platform.web.common.exceptionhandling.NuxeoExceptionFilter.handleException(NuxeoExceptionFilter.java:55)
at org.nuxeo.ecm.platform.web.common.exceptionhandling.NuxeoExceptionFilter.doFilter(NuxeoExceptionFilter.java:64)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:96)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:230)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
at org.jboss.web.tomcat.security.SecurityAssociationValve.invoke(SecurityAssociationValve.java:182)
at org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValve.java:84)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.jboss.web.tomcat.service.jca.CachedConnectionValve.invoke(CachedConnectionValve.java:157)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:262)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:446)
at java.lang.Thread.run(Thread.java:619)