Changes in the serialization code in Merlin break applications that override the writeClassDescriptor/readClassDescriptor methods. This prevents Weblogic from running at all.

The attachments contain 3 files: a class that implements a simple object input stream, an object output stream, and a test program. The test program runs fine on 1.3.0 and 1.3.1; it gets the following exception in Merlin:
Exception in thread "main" java.lang.NullPointerException
        at java.io.ObjectStreamClass.initNonProxy(ObjectStreamClass.java:375)
        at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:1441)
        at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1357)
        at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1544)
        at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1202)
        at java.io.ObjectInputStream.readObject(ObjectInputStream.java:297)
        at Test.main(Test.java:28)

This is with build 65 of Merlin.