Voices through speakers not working in BootCamp, but in OS X., Voices through speakers not working in BootCamp, but in OS X.

I have the Pioneer VSX-1021 and when rinning OS X, the sound works perfect (running 5.1). When I switch over to Windows 7, the voices all of a sudden cut out. The rest of the audio works fine, but the voices get muffled. I'm using Realtek, and have all of the drivers updated. Does anyone else have this problem?

Mac pro is the mid 2010 model

Small Klipsch speakers if that matters