More details please, including the entire exception stacktrace and the console logs. Also post your ejb-jar.xml, jboss.xml(if any) and the relevant bean code.
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P.S: There's a forum specifically for JBossAS5 questions http://www.jboss.com/index.html?module=bb&op=viewforum&f=287
I created a skeleton EJB/EAR replicating the one I want to use (but minus the added application). This works fine in all of the JBoss version.
I would like to know if this could indicate a problem with the dependencies?
If my EJB contains jars that clash with the JBoss ones would this cause such an error?