Yes all of my imports are the Java.util implementation of the hashset.
This line from your stacktrace gives a different story. "Caused by: com.google.gwt.user.client.rpc.SerializationException: Type '*org.datanucleus.sco.backed.**HashSet'* -- You received this message because you are subscribed to the Google Groups "Google Web Toolkit" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/google-web-toolkit?hl=en.
