Averatec 3200 - Mobo issues?

I had a Mobo replaced by Circuit City's repair depot due to the power connection becoming loose. Around a month after this the machine's fan begin to rev up ..then flutter a little, then Windows would freeze. Upon reboot I would not see the Averatec Splash screen or windows loading. You could just hear the fan running, not hard drive lights flashing, the display appears to be off as though the machine isn't on ( not a back light issue) nothing. If you let it sit for a few hours, eventually the hard drive light starts flashing and it boots fine...only to freeze again hours/mins or days later and go through the whole process again.
Needless to say, I have sent this unit back ( to circuit city) 4 times now and every time get the same response...nothing wrong. Before returning it last time I reimage it back to factory spec and flashed the bios...but the issues ( freeze, reboot, no splash, no nothing) still happens. The only thing that has changed has been the Fan now seems to work ok. Oh and the last time the tech reimage it as his solution, even though the call clearly stated the machine had just been imaged to factory spec.

Any thoughts on this one? I am not crazy...this is a faulty mobo is it not?
The problem is intermittent so I understand it can be a problem to trouble shoot for the techs.
****I stated that the mobo was replaced as this is what was quoted on the repair sheet, if they just replaced the power plug board, replacing the mobo too would be a bit odd, but thats what was on the work order.

Thanks
J