My guess is the client and server code are out of sync. Pull the new client jars down to you client deployment and it will ... start working again.
I switched the libraries to the correct newer files and ran the client program and it worked great.
marc fleury explains:
The client side classes were under great movement, so we apologize for the fact that unmarshalling on old classes will throw exceptions. The classes are stabilized now but we will optimize the writing of it (work underway as we speak) as optimized writers bring about a 30% increase in speed. So you might see more of that in the future.