This problem comes up quite frequently.
Java requires the serialVersionUID of the class to be identical on the object sent across the network by RMI and the locally loaded class that is meant to rebuild the object.
As you are using two different versions of JBoss, you are getting diferent serialVersionUID's.
As you have already guessed, you need to use the same version of JBoss at both ends of the network connection.
There are other reasons to use the same version. There may be undocumented changes of behaviour between different versions of JBoss.
You could also look at using web services rather than RMI for this scenario.