I built this machine a year ago, worked fine except once or twice, when turning it on I'd have the jostle it around or reseat the video card to get it to boot.
I tried reseating the ram, nothing going.
Subtle hint:
If I don't have the monitor cable plugged into the card, machine reboots several times in quick succession and then once every half second or so.
If I do have the cable plugged in, the first quick succession does not occur, only the longer half second reboots.