Couple of questions:
1. What program did you use to record the tracks with?
2. Which program are you using now?
3. Which format were the tracks recorded in?
4. How did you transfer the 12 tracks to your friends mac to begin with?
If you can answer these i'll try and help you out more.
The only thing obvious that I can think of the now is that the tracks aren't in .wav format and are in .aiff format which are mac based. If this is the case you would need to convert the audio tracks to .wav.