mm2 distorts sounds or won't play at all

I have been working on a mm project for my family that is
using strickly pictures (no movie clips) and sound. I
was using .wav files and everything was working fine.
When I came back to the project a few days later only 2
of the 20 sounds I used worked properly. The rest either
played at 2-3x the speed or it just sound like a squelchy
white noise. I found that the 2 sounds that did work
were mp3's. Soooooooo, I changed my sounds to mp3s' but
excluding the 2 mp3's that originally worked all the
mp3's are doing the same thing. I have tried everything
that I can think of. I have made no recent changed to MM
and infact updated it to MM2 to see if it would solve the
problem, which it didn't.......ANY HELP WOULD BE GREATLY
APPRECIATED!!!!