I had the same problem . I have deployed my ejb's on both jboss 3.2.X and jboss 4.X. I have tried to call the ejb from my java client using eclipse. I can access the ejb in jboss 3.2.x, but if i try to access the ejb on jboss 4.X i got the error saying that the '[Root exception is java.io.InvalidClassException: org.jboss.util
.id.GUID; local class incompatible:' . But i did a mistake that my client classpath was pointing to the jboss 3.2.x jbossall-client.jar.Then i changed it to point jboss 4.x jar. Now its working fine. Apply the same for your cases too.
Thanks & Regards