I understand this is a very annoying bug and I agree that it's impossible to watch a movie like this.
HOWEVER, I don't know ANY media player that can handle VBR MP3 without any trouble, not even WMP!
Therefore, instead of waiting for a fix (which could probably really take a while), I would recommend you simply convert your MP3 to a CBR file, at a bitrate of 128 or so.
A lot of programs allow you to do that pretty quickly (but make sure you pick one that DIRECTLY converts the MP3 file instead of making a WAV from it first (unless you got time and 1GB / hour of audio free HD space).
I recommend
MP3 workshop, a freeware tool that offers all sorts of MP3 editing.
IMHO this is NOT a critical bug that has to be fixed ASAP. I'm sorry that I keep telling people to find an other way to handle their problems, but I am eagerly expecting a stable BSPlayer 1.0 version and if Bst2k has to handle 1'000 bugfixes first, it's not gonna be released anytime soon...
Cheers, Smarties :P