Also in the Recovery Console there is an option to Fixboot. I have found on a couple of occasions that even if the Chkdsk has run OK it needs to create a new boot file.
Fixboot does this for you. I've rescued a couple of PC's this way, although it does sound to me to be like a power issue.

One of the other things to check is the Capacitors on the mother board. I've had very simular issues when I've had a blown capacitor on the Mother board, you can tell if they are kabut as the tops will be raised and you'll often see some leakage.

Good luck with it.