Sorry for the delay (finals week at Caltech).
I downloaded and installed 2.2.2, and the weird bug (at least, the one that I initially heard) is still there. I hear it in Credits_Music.it and Quotes_Music.it, and it's probably in other tracks as well (I listened to Credits and Quotes a lot before Winamp 2.7 so I know how they sound, and also listened to them in game).
Here's exactly what I'm hearing in the hopes that it will help in finding this evil bug:
In Credits_Music.it, it goes, eh,
"Chicka-chicka Boomp Chicka-chicka *pause* Boomp-Whoooooo....", where the "whoooo" is at about 2 seconds into the song. The way it's supposed to sound is a smoothly fading "whooo" sound. In Winamp 2.7 and later, halfway into this "whoo" sound, it drops in volume by like a half, very abrupt and noticable. I hear it with headphones and the 2-speaker (normal) stereo mode of my Altec Lansing ADA-880 speakers. And when in 4-speaker Dolby Surround mode, how I usually listen to music, the entire sound sounds extremely hollow and corrupt, worse than even the worst MP3s I've seen. In headphones and normal stereo, Quotes_Music sounds extremely corrupt: sounds are truncated and blippy (I don't know how to exactly put it).
The .IT files that my converter produced show up as Impulse Tracker 2.17 in Winamp's File Info box.
Hope this helps,