Sounds like A) a bad pointer (could mean a lot of things) or B) the OGG decoding code isn't working correctly.
Mr.Fury's been having problems with OGG stuff, too, I think. taylor and I have both gone over the code at least once and haven't seen anything wrong with it, I'll probably be going over it again this weekend.
In the meantime, any patterns or errors you can find would be helpful. Something like 'When an OGG file is supposed to be played, the sound/music track before it in the tbl is played instead.' or 'it fudges up when X happens' would be handy (Which actually might be true) or 'variable bitrate files don't play right' or 'the numbers in music.tbl are wrong'
You could also try manually setting sound quality with this build:
http://www.hard-light.net/forums/index.php/topic,29352.0.htmlThe code should also be in my not-typical build, but people have been trouble with pilots not working.