Could be an overheating issue or a PSU going bad. After running for a couple hours, do a reboot, go into BIOS (usually by pressing F2) and record the temps and voltages.
You could also unplug it, open it up and check out how clean the fans and heatsinks are, though I would have thought a new mobo would have caused a good cleaning.
Dell says a blinking amber light indicates a power supply problem.
You could also unplug it, open it up and check out how clean the fans and heatsinks are, though I would have thought a new mobo would have caused a good cleaning.
Dell says a blinking amber light indicates a power supply problem.