Usually when Pocket Tunes crashes on startup it is because you have a corrupt audio file installed. When Pocket Tunes first starts, it scans your expansion card for audio files, then sorts them automatically by Album/Artist/Genre etc. If it encounters a corrupt file during this scan, it cannot get past that point so you have a crash.

If you have a crash and have NO audio files installed, then the problem is usually a corrupt file system on the expansion card. Format your card with the "Card Info" application. That should solve the problem. Be sure to back up any important files you have stored on the card first!