I'm assuming that you are using JBoss3x and running on jdk 1.3 or greater for the server. The problem you are seeing has to do with RMI communication between 1.3VMs and <1.3 VMs. In 1.3, Sun added support for RMI serialization of strings greater than 64k. However, when a 1.2.2 JVM attempts to read a string greater than 64k from a 1.3+ JVM, the 1.2.2 JVM will throw the java.io.StreamCorruptedException.
Unfortunately, I don't know of a good way around this problem using RMI. You may be able to use IIOP for your cross VM communication protocol, though I haven't tried it myself.
Hope that helps.
Many Thanks Mike!