forgot to mention, I'm using 1.4.0 beta
This problem was of my creation. It's fixed, and the modified versions of SimpleClient and SimpleServer, as you described them, work.
If you're working off CVS, you can get the corrected versions of CompressingMarshaller and CompressingUnmarshaller from the HEAD branch. Otherwise, they will be included in the 1.4.0 Final release, which should be out in the very near future.