Hi! Have you resolved this ? We also use JBoss 4.0.4GA and have an even weirder problem. One bean method loads an object via hibernate and it works. After some time it throws ....MappingException: Unknown entity Foo That is, the same method once works, then later throws a mapping exception ... If we restart jboss, it works again for a while. David View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4100580#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...