I'm starting to think that maybe the conversion to Flash video used by both Vimeo and YouTube just can't handle audio well. In this case YouTube seems even worse than Vimeo, but both introduce some nasty distortion. I'll post .wma files (like I did for Maiden) so that there's an accessible version of decent-quality audio. I think if you download the .wmv from Vimeo, you'll also get decent audio.
Chopin: Etude Op.10 No.3 from Ken Barker on Vimeo.