Games keep swithcing my audio back to 2 speakers?

hey all,
I have a minor, but somewhat frustrating problem on my hands.
I use my onboard Nforce2 (in sig) audio, and have a 6-piece speaker set-up. Nautrally, in the Nforce speaker setup panel, i select "6 speakers".
However, whenever i go into a game, play for awhile, and quit back out to the desktop, for some reason my setup is always taken back to '2 speakers' and I have to go into the control panel and keep resetting the settings.
Does anyone know what would cause this? Its getting kind of annoying.

P.S. It seems that certain games don't suffer from this problem. But games like neverwinter nights and Mafia constantly do it. Mafia will not even support surrond sound in the game for me. :(