On Exception, the IN_CONTAINER TestRunner tries to serialize the caught Exception back to the Client so it can be displayed as if it was local. The problem is if you don't have the Client lib on Client Classpath or you have the wrong version of it. This results in a Deserialization exception on the Client.

We probably have to not Serialize the actual Exception, but serialize a Textual representation of it, which we can create a 'proxy' Exception of on the client side and make it 'look' like the original.