I am quite sure the Corba-Services are thread safe. They are not the origin of the Problem. We made some tests with thousand of messages sent to the message queues from multiple Clients in parallel. Most of the time all went fine. In let's say 1 of 20 bulk tests the failure situation occurs. There is no indication why this happens. There has to be a buggy module inside the JMS subsystem. We have to investigate more effort in order to solve or workaround this problem. Meanwhile we have to restart the server when the problem occurs. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=3990006#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...