Now I tried to run my app WITH jboss-common-jdbc-wrapper.jar and WITHOUT jboss-ejb3-all.jar. This works, too. So it looks like those two just hate each other ;). I had added the jboss-ejb3-all.jar due to an exception (see above) that I had with the CVS version of Seam. But as I switched to "normal" Seam now this exception doesn't emerge anymore, so there seems to be no need for this JAR (in opposition to what Gavin said in the thread I mentioned in my first post). View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=3958504#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...