This basically happens whenever something goes wrong.
It can mean anything from a missing file to one without a proper .rel to a bad renaming of one of the files. If it's in the middle of a match, I'd go through all of your fighter/stage files and make sure they're all named correctly by checking with me or someone who's had a lot of success with using hacks. If something STILL doesn't work, back up everything important on your SD card and format the thing, then put everything back on. If THAT doesn't work, one of the files might have been corrupted and A) should be redowloaded or B) reported if nothing else works. If NONE of this stuff works, get back to me through this thread or a PM.
Problem SOLVED! there was a few bad brstms in my strm folder. It froze because when it reaches a certain part of the song it was corrupted, so i removed all my custom music and re added the working ones. Works like a charm!