Hey Louis! I have the same problem. I installed Switch and imported a cd with mp4. then I converted it to mp3 and pushed 'play'. Nothing. then I had Switch overwrite the songs and it saved them in my documents file. From there I imported a couple to i-tunes, pushed 'play'... nothing. No sound; it ran without sound.
then I coverted the song again in i-tunes, pushed 'play'.... no sound.
I saw that there is no mp4 format mentioned in the list, so I think it just doesn't work. Any suggestions, anyone?!?
Gerhard