5.1 sound in Vice City

[beatle]

I have an NF7-S and I'm using the soundstorm optical output to get 5.1 on my receiver. This works great for games and mp3s with the exception of GTA-VC. In this, it resets my speaker setup to 4 speakers, so that I no longer get sound from my center channel. I then have to change it back to 6 speakers in the nvidia control panel if I want my center back for windows/other games. I've tried the other sound modes other than EAX with no solution. Is this a known problem with a fix or is it just something I'm going to have to deal with until a patch comes out?