I believe I've just had a 2nd motherboard failure in the 3 weeks that I've had my new computer. Both times they failed after I tried to restart my pc after it had been running for awhile. Basically, all it will do is boot for 5-20 seconds, and then reboot over and over until I unplug it. It gets stuck at the Gigabyte screen, if it makes it that far. This time around I can at least get a POST error beep if I remove my ram. The only thing I've done so far is remove CMOS battery and reset the BIOS via jumper. This is probably the 10th or so PC I've built over the years and I've never had problems like this.
Here's my specs:
I7 2700k
Gigabyte Z68X UD3H-B3
8gb Gskill ram
750gb Caviar Black
EVGA NVidia 570GTX
Corsair TX650 PSU
Thermaltake Frio cooler with 1 fan currently installed.