Tomcat 6.0.2 and 6.0.14 (although less frequent) will send a HTTP 500 message because of this error:

 java.util.ConcurrentModificationException
     at java.util.HashMap$HashIterator.nextEntry(HashMap.java:787)
     at java.util.HashMap$KeyIterator.next(HashMap.java:823)
     at org.apache.catalina.util.Enumerator.<init>(Enumerator.java:101)
     at org.apache.catalina.util.Enumerator.<init>(Enumerator.java:67)
     at org.apache.catalina.connector.Request.getAttributeNames(Request.java:929)
     at org.apache.catalina.connector.RequestFacade.getAttributeNames(RequestFacade.java:277)
     at com.sun.faces.application.WebappLifecycleListener.requestDestroyed(WebappLifecycleListener.java:76)
     at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:188)
     at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
     at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:105)
     at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
     at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:212)
     at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:818)
     at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:624)
     at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:445)
     at java.lang.Thread.run(Thread.java:613)

When the bridge receives the error message it'll just shutdown. The server is not aware of this and it will happily queue the generated updates creating this pseudo memory leak.