*scratches her head* Ok, this just gets more and more bizarre...
I definitely had 24 FPS compressed audio, not 23.976 compressed audio, attached to my 24 FPS AMV. So that wasn't the problem.
Bizarreness: scrupulously watching my out-of-synch version and my in-synch version side by side, I am now finding it very difficult to see any synch issues with the former. This is maddening, because I know there were a number of places where the synch was off enough to make me cringe. What's changed? I have no idea.
I'm beginning to think that - for some reason - computers are occasionally having a harder time with the MP3 audio than the WAV audio. I've never seen the original WAV file out of synch, for whatever that's worth. This is fairly relieving (seems apparent I didn't mess up the audio), but also very worrying (something else
is messing up the audio).
I'm going to keep an eye on this and see if the synch devolves again. I won't continue to fuss about it publicly, though, unless I figure out what the hell is going on.
Kero - if you're keeping tabs on this, I suggest you also try viewing your AMV on someone else's computer. I have no idea how bad your synch issue is, but if it's not too horrendous, it might be worth a shot.