You are running out of available listeners to service incoming web requests for your Jetty servlet container. Try modifying/increasing the maximum number of listeners available to service HTTP 1.1 persistent connections.
Modify server/instance/deploy/jbossweb-jetty.sar/META-INF/jboss-service.xml (JBoss 3.2.x or higher):
Or an appropriate maximum. Do not change the minimum (MinThreads) to be equal to or greater than the MaxThreads value as the MinThreads value is the minimum number of free listeners, not the minimum number of listeners (according to the source code).