I get the exception message: "Error deploying bad magic number: cba78dd8" The EJB (in the EAR) is fairly basic and I have tried to keep it as minimal as possible; There is a class which implements @Remote & @Local interfaces. The ejb-jar.xml file looks like this: <enterprise-beans> <display-name>xxx</display-name> <ejb-name>xxx</ejb-name> <ejb-class>com.xxx.xxx.xx</ejb-class> <session-type>Stateless</session-type> </enterprise-beans> As the title states, this EAR works on 4.2.2 & 4.2.3. All help appreciated! Thanks View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4198031#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...