I have the same problem (Windows 7, M-Audio Fast Track Ultra)
I don't really have a 'surround sound' option to experiment with switching on and off, I have a multi-channel setup for recording music. Judging by the above comments, I guess the game sends surround sound and stereo sound to non-standard channels?
In that case, I hope they patch it! I can't really be bothered swapping my settings or speakers around each time I play the game. For now I just turn up the volume very very loud and it sounds great... but all hell breaks loose if I forget to turn it down after playing
