A few days back, I was struggling with running the RMI Client against the CreditRatingService with a fault scenario. [setting ssn=0].
I was receiving an UnmarshallException whose root cause was an "InvalidClassException" referring to the class javax.xml.namespace.QName.
On further analysis, I discovered that JDK 1.5 ships with a javax.xml.namespace.QName that carries a different serialVersionUID than the one that ships with JDK 1.4.
Since I was using JDK 1.5_06 to run my RMI Client, it kept on complaining.