if i where you, i would access the CF card via usb, if it doesnt freeze your mpc, transfer the files you need off the card, if you dont know what something is, leave it on the card. then format the card with the mpc. now try a new folder. if it doesnt freeze, start moving data back to the card. if it freezes after that, you got a bad file in there causeing it. now format again, and start moving back one file at a time, testing with trying to create a new folder each time, until you hit he bad file.
best i can do for you man, its a **** but worth a shot, that or get another CF card, and format it and try it out maybe?
Rob