Hi Werner,
Well, I'm not sure what is going wrong, but I can describe the context.
When the client does an invocation and there is no existing pooled connection, a new socket is created, on both the client side and the server side. The client side creates an ObjectOutputStream and the server side creates a matching ObjectInputStream. When the ObjectOutputStream is created, some header bytes are written, and the ObjectInputStream's constructor tries to read them. For some reason, it is unable to read the header bytes, and eventually it times out.
So you should look for something in your system that is preventing those header bytes from getting to the server.
-Ron