Midi stop working in the middle of recording!!!

[Freeze]

I'm a novice and I just put together my computer. 2800+ amd processor. 1 gig of ddr ram. etc.
I hooked everything up and to my surprise it worked. I have a mbox with 5.3.3 LE.

I usually make my music using my mpc as a sequencer and my motif as a sound module and a controller. I then use my protools as the master and slave the mpc via midi clock. One track at a time. It's been a flawless operation. After I assembled the new computer, I recorded one entire song which consisted of about 13 individual music tracks...no problems.

The problems began on the next song. I recorded 3 tracks...4 bars a piece and it stopped working! I couldn't get it to start the mpc. I could start the mpc manually and the protools program would still play and record but it wouldn't start the mpc. I tried everything...to no avail. Finally I shut the computer down and waited 5 sec, restarted and then it worked fine. BUT ONLY FOR 3 MORE TRACKS!!! Then I get the same problem. The midi doesn't work anymore. No error messages or anything! Some one please help!!!

ps I'm a newbie and yes I searched the past thread and couldn't find any relief