I am upgrading from JBoss 4.0.5GA to 4.2.1.GA. I am also using Seam 1.2.1GA. The server came up fine. It's the client that I am trying to bring up that threw this exception. My client references all the jar files reside in the jboss-4.2.1.GA\client directory. Perhaps these jars conflict with each other? Do you know the minimal set of jar files I need if I only do EJB + JSF? Thanks -tony View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4067505#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...