Hi Lloyd,
I know theres a known issue/conflict with the ms audio mapper and the realtek audio card in xp, but i dont use vista and i dont know if you have realtek, but the concept may apply. In the realtek case, the microsoft mapper seemed to be in conflict with the realtek drivers and some programs got caught in the conflict. to resolve that issue, the drivers had to be updated and the mapper had to be tweaked. Again, I'm not sure if this applies but maybe it might give you an idea where to look ?
good luck.
~R