How about your other bump maps -- do any of them work? It's gotta be either the map, the model, or the program. If other maps work on that model, it's probably the map. If the muscle maps work on other models, it's probably the model. Since it's doing the same thing on two computers, it's probably not the program.

Does 3D Studio Max allow you to import BVH motion files? If so, you could export the BVH, save 1 frame of the figure as a .3DS, then reassign the BVH to it in Studio Max. If not, that's a fairly useless suggestion. :^)

Well, the stomach muscles seem to show up okay... I haven't use P2 in forever, but does it have an intensity slider for the bump maps? Any chance your figure is a downloaded one with a different UV map?

That's happened to me, too, and I've seen a few other references to it. I've gotten in the habit of saving the .pz3 files I've used to develop the character until I've tried bringing it back in from the character library, just so I have a backup.