java.lang.RuntimeException: No ClassLoaders found for: net.sf.hibernate.collection.Se

java.lang.RuntimeException: No ClassLoaders found for: net.sf.hibernate.collection.Set

Hi All,

I am migrating my project from hibernate2 to Hibernate3.6.
Please note that I have 2 JBoss servers that talk yo each other.
The project deployed on Server 1 (say 'A') is still on Hibernate2, while I have migrated the projetc on server 2(say 'B') to Hibernate3.6.
Now, an object constructed at 'A' is sent to 'B' and I am getting the above mentioned Exception a 'B'. Seems the Exception is coming while deserializing the Object at 'B' which was serialized at 'A'.

Can somebody help me out with :
1. Solution to the above problem
2. Is Hibernate 3 fully backward-compatible with Hibernate 2?

The stack Trace:
12:49:07,882 WARN [root] Clone and Redelivery property not set as expected.
12:49:08,890 ERROR [root] java.lang.RuntimeException: No ClassLoaders found for: net.sf.hibernate.collection.Set
at org.jboss.mx.loading.LoadMgr3.beginLoadTask(LoadMg r3.java:306)
at org.jboss.mx.loading.RepositoryClassLoader.loadCla ssImpl(RepositoryClassLoader.java:521)
at org.jboss.mx.loading.RepositoryClassLoader.loadCla ss(RepositoryClassLoader.java:415)
at java.lang.ClassLoader.loadClass(ClassLoader.java:3 56)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:264)
at java.io.ObjectInputStream.resolveClass(ObjectInput Stream.java:622)

Thanks,
Shishir