My customer is receiving the following message after upgrading to 6u7 or upper:

org/omg/CORBA/MARSHAL: CORBA MARSHAL 0 No; nested exception is:
org.omg.CORBA.MARSHAL: can't deserialize enum vmcid: 0x0 minor code: 0 completed: No 

We should document the following adviced I found in case 66005672:

Customer need to take care those type in their code, use other acceptable type to substitute Enum in RMI-IIOP. He should use a class to represent the Enum type and within the class use static integers to represent the Enum type value. Then when serialize, use the representation not the Enum. Enum is not recognized in serialization in RMI-IIOP.