2 related forum links:
http://www.gnutellaforums.com/showth...ight=C00D11%2A http://www.gnutellaforums.com/showth...hlight=C00D%2A
The 2nd of which is a different error but my link posted earlier ends up at same site as Norbie's link.
I've a suspicion VLC & MPlayer might be able to play those files. VLC also plays audio file types:
http://www.videolan.org/vlc/features.html
AFAIK The problem with WMP is it doesn't provide sufficient codec support on its own (or even from its own MS codec site.) I'm aware that the 3ivx codec is supposed to add extra audio (as well as video) support such as m4a, etc. for WMP.
I might be wrong but worth a try.