In the past (http://www.jboss.com/index.html?module=bb&op=viewtopic&t=133202), we have got the Hibernate version upgrade working in JBoss-4.2.x, so i know it works. But, i don't exactly know what's the problem with your setup. Right now, its too late in the night for me to think about other possible reasons why its not working. In the meantime, post the verbose class logs and also the output of: jar -tf yourapp.ear I'll look at it with a fresh mind, sometime during the weekend and see if those logs and the ear listing helps in understanding what's wrong. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4170842#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...