Direct Show Problem

[Teslacuted]

I transcoded the .ac3 of Star Wars, Episode 2 into a 5.1 Ogg (-q 0.300 -6ch) using BeSweet GUI 0.6 b75, the file plays perfectly in Winamp but when I try to play it in WMP or the full movie with it muxed it sounds like there is vocal masking on (music and sound effects are perfect but the voices are dimmed and have echos), as far as I can see this is due to Direct Show as it doesn't load with Winamp, I've tried re-installing and I can't see any settings in the Vorbis Decoder that would cause this, anyone know the solution?

[Edit] Could it be that the sound isn't being correctly downmixed? I have a Soundblaster 5.1 but only a 2.1 setup and when I only have 2 channels (-q 0.300) it sounds fine.

Thanks,

Teslacuted