I've got the same problem. I got a GIGABYTE motherboard GA-P35-DS4 with Socket 775, but there's two different rev. versions that I don't know the difference on. I've tried them both.
The first install worked(don't know what that version was), but after a few days of happiness over my sound working properly, I left my computer for a second, and the sound dissappears. I've tried both versions, uninstalled and installed, but nothing works. It has turned out sometimes, that I'd get my right speaker to work, but eventually it looks like the software doesn't seem to know, what input I'm using. One day I got it all working, but after some minutes the sound took off in small bits again(weird).
if anyone has the same problem, please answer and tell me what version I have to install, it's kinda getting me on the nerves.