Midi pain in the butt

[switchbitch]

I have been using my indigo 2 with akai mpc2000xl for over a year. Today I uploaded the song onto my akai mpc from the external hard drive. Everything appears to be how I left it. I created a song in multi single mode. I play back the song using the akai as master as usual and all the parts are playing (Im only using three parts) but now when I try to record another part on a different track it does not record or playback the part. So I can play back what I did last time but for some reason it appears as though no midi data is being transmitted on the new tracks. I have checked that Im using the right channels, I checked numerous midi settings etc but nothing. Can anyone please suggest any solution for this?? Thankyou