there was a newer version of brawlvault (cant remember which sorry) that completely ****ed with BRSTM making and made them static in-game, even after reformatting, defragging, remaking the brstm, etc etc
i currently use version 63.d for brstm making (its all i use it for), and its been perfect otherwise
ALSO, what are you using to convert your songs to WAV? That might be causing the problem, I personally recommend you use foobar (as a music player, and for converting formats, its fast and easy), its given me the best results compared other methods (converting in itunes, using that old audacity method, etc ect)