The UIL2 org.jboss.mq.il.uil2.UILServerILService connection accept thread (UILServerILService Accept Thread) can exit prematurely if there is any exception other than the expected java.io.IOException. Runtime errors like java.lang.OutOfMemory due to recoverable resource exhuastion like too many threads can cause the thread to exit with the result being that no further jms connection can be made. The jms client would see an error like the following in this case:

org.jboss.mq.SpyJMSException: Cannot authenticate user; - nested throwable: (java.net.SocketException: Connection reset)