Did the character attributes reset, as well, when your friend took control of the character? This is a known, relatively rare issue (less rare in Classic than it was in the Enhanced Edition).
When this happens, reloading the save, possibly multiple times, should get the character loaded properly on the client system. One person said it help to join in an older save, and then load the most recent. You could also try creating a new profile and starting a new game.
A temporary stat boost, such as from the Man At Arms skill Encourage, may also reset the attributes on the client system.
