The error is not very detailed, but it looks like it is a "couldNotFindClass" type error. Since the class is weaved, do you have the JPA provider classes on the client side classpath? This would be the toplink-essentials.jar for Essentials.
Best Regards,
Chris
[Message sent by forum member 'chris_delahunt' (chris_delahunt)]
http://forums.java.net/jive/thread.jspa?messageID=294408