No yellow question marks in device manager?
I'm stumped. Might be TS, or a possible buffer overload (my old 5.1 setup had issues, so I had to drop to 4.0 when using a Razer Barracuda...).
Also, is it just sound input, or is output also affected? Also, does using a mic input from within a game working correctly.
Again, I'm clueless, but maybe I'll think of something...