Mizuka

I couldn't find another topic about this, forgive me if I've accidentally skipped one. Here goes... Most of my music is in mp3 format, but the few times I had mp4 files, SonicStage would have an error message pop up and tell me that the file isn't supported by SonicStage. SonicStage is supposed to be able to play mp4 audio though, right? The only thing I can think of that would cause this problem would be if the files weren't real mp4s, but I can't think of a file that SonicStage can't play and Winamp can. Is there anyone else who had this problem? Is there any way to fix it?