If I remove them everthing would work fine! But that would lead to the problem that all EAR Projects on the production server use the same Hibernate version. On our production machine we have about 20 projects using different versions of hibernate (some still use hibernate 2). Some other projects are evaluating toplink. I don't want to set up a new JBoss Instance for every version of any JPA Provider in use on our server. If that would be the case I would reccomend to step back to using hibernate without JPA. You could also remove the classloader isolation with all the drawbacks you will have. But thanks for the response! View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4054736#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...