Have you tried updating your audio drivers
? May not do much or even anything but if you haven't... it is another option you didn't have before.
Do the headsets work with just regular music? I mean, have you test the headsets before starting the game?
My friend was having the same issue with the latest CoD Black Ops game, sometimes the Game Audio Option for the headsets would work, other times it wouldn't. It may not be your pc but an internal problem with the game... perhaps there are new patches for the game?