Publisher 2000 and 2002 compatibility

This is a simple question. A user has Publisher 2002 on one machine and saves a Publisher file on the Shared drive. She then goes to another machine that has Publisher 2000. She can’t open the file with Publisher 2000 – even when she originally saved the Publisher file as a 2000 version when on Publisher 2002 (the first comptuter. Are these versions simply incompatible?? Is there a fix for this???
Matthew