I managed to find out what was going on. What I did was download the hibernate source. Stopped at the exception ponit with the debugger and found out which instance was causing the problem. As it turned out it was a vairable which existed in a super process which I have not taken care of. Now everything is all right. So.... Remember that usually the problem is with your variables, and they can exist in a super process too. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=3987724#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...