Could be a channel board. have you tried running the basic user diagnostics on the system? the comprehensive test.
if you feel adventurous you can try pulling off that front connector board, and behind that is the AIM board, along with the channel boards. try re-seating (pulling out, and putting back in) those, and the FEC. make sure the machine is unplugged from the wall prior to doing all this... of course.
if you can get some sort of static shielding, i'd recommend that as well... but if you can't, try not to touch any components on the boards.
I'll ask around with some of the engineers and see if they've come across this intermittent issue before.
Universal Diagnostic Solutions