I've been receiving MP3 files from the musician for my project and MMF will play these files fine as samples. However, I had opened some up in Audacity and cut them, exported under default settings and MMF just freaks out when playing them. They will crackle or stutter and seem to speed up for unknown reasons.
I've managed to cut things in audacity before and it played in MMF correctly. Any idea why it's getting so upset? WMP will play the files correctly by the way.
Check the bit rate when you're saving it. That's the only thing I can think of. MMF might be having trouble playing it if it has a variable bit rate. A constant bit rate of 160 or 192 should be fine.