So a 3 minute long music file (say) will play in (for example) 2 and a half minutes, but at the same pitch as the original? I'd like to make sure I understand your problem. It might actually be helpful to post timing results.
Also, does this happen with every sound (wav, mp3, ogg, playing direct from CD) or just some of them? If you have NTFS support in your kernel, try mounting your windows drive(s) and playing some WAVs you'd actuall hear in Windows, for a one-to-one comparison.