Sudden shut off after gaming - Won't start at all

[earvinarp]

My computer shut off quite suddenly after playing Starcraft 2 on ultra for about 2 hours.

The system is an i7-3770k on a p8z77-v deluxe, running at 4Gb OC (only .1 over the stock), vcore at 1.16v (quite low to prevent heating - seemed stable), 8GB RAM. It has 2 AMD HD 7770 GPUs and a SeaSonic M12II 620 Bronze 620W PSU. The whole system is 2 months old.

Truth is that temperatures were a bit high, as I have been running only the stock cooler of the cpu plus 2 case fans. It was idling at around 50C and, when under load, could reach 85C but would operate in the 70s mostly. I know that 85C is only 20C off the cpu's max but, if my understanding is correct, the ivy bridge does run hotter than others.

When I try to restart the system, the PSU and the CPU fans both make a faint attempt to start but stop immediately.

Now, I have tested the PSU and it seems fine. Any idea of what I am dealing with here? My suspicion is the CPU but, would that prevent the computer from waking up at all? Is there a protection mechanism in the mobo that I am missing?

Thank you in advance for any feedback.

 

[earvinarp]

Actually, I took it all apart and it seems to be one of the GPUs. When I plug it either alone or along with the other one, the computer will not start. Is it safe to assume the GPU is consequently done? Thanks

EDIT: even though considering that the failure happens right on startup, would it not be a short circuit in the GPU that immediately tells the mobo to shut off? Considering that, would be it be possible that the card were still ok? I am very tempted to open this thing up.