> I am using JBoss 3.2.2 RC4. Everytime when I try to
> send a null value e.g. of a String to the client I
> receive an unknown exception.
Please give more details. How are you sending null to the client? I have run a simple test that in which a String-valued EJB method returns null to the client and no exception was thrown. Did the same from a Foo-valued EJB method (where Foo implements java.io.Serializable), also with no problems. For these tests I have used Branch_3_2 from CVS, but see no reason 3.2.2 RC4 should behave differently.