Ya, that is what I was thinking. Have you checked any BIOS settings (power saving, etc) that could cause this? It could be the motherboard. I had this same problem, but it ended up just being BIOS settings and an unstable overclock.
I was thinking it was my overclock until I put it at stock settings and it did the same thing. I might roll with the software thing for now and if I can't figure it out by this weekend, do a fresh install.
Well, I mean I didn't technically solve the problem, as I still get vdroop and the board has bad voltage regulation in general, but I fixed it to work for my needs without replacing the mobo. Now, I have a Sabertooth 990fx that needs to get RMA'd.