I am getting the exact same error using the default db hypersonic. This occurs during my long running test that I have setup to send 10 million messages from 3 different JMS clients. The test is set up to send batches of 1000 messages and sleep for 10 seconds. The messages are received by a message driven bean and a log message is created for every 1000 messages recieved. I am not performing any other business logic. After about 2 million messages, I get a NullPointer exception on the server side and a unique constraint violation on the client side. Any ideas here? View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=3966433#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...