P965-DS3, can't restart/reboot?!

I've got one P965-DS3 that was running fine for the past 1/2 years. now, all in a sudden, it can't restart or cold start?! I pull the battery out, and it can boot up again. and runs fine in vista even fold 24/7. but as soon as I hit restart/shutoff, it can't boot up again. and sometimes, unplug the power for a min or two works, sometimes need to pull the battery. system is running at stock btw.

what's wrong??? this is driving me nut now.....

Try pull one of the memory and use single stick of RAM to see if there is any different.

already swapped the firestix in it to ballistix, same thing.....