Video card shuts off randomly

[Sceptrum]

Hello,
My issue is very strange, i try to explain it properly. At the beginnig, my monitor randomly went black, and shows "No Displayport Cable" during playing game. When it happened, the VGA whizzed up, and stops. Strange another symptom, when i switched off my computer, the monitor also shows "No Displayport Cable" instead of "Enter Power Save Mode" than before. I sent my VGA to warranty service, i got it back, but it happened again. After that a renew my displayport cable, and the "No Displayport Cable" phenomenom gone, but my videocard still shuts off, and now, not just during games, in idle, too. I don't think it's an overheating issue in idle.
i tried monitoring temperatures, in the last seconds are weird results. 37000 C (not exactly) on 3 sensors, -0,4 Mhz on GPU clock, and so on.
Any help will be appreciated. Thanks.

 

[Sceptrum]

In addition:
I completely reinstalled Windows, formatted all hard drives and SSD.
My Spec:
Cooler Master Cosmos S RC-1100 | Asus P6X58D-E | Intel Core i7 930 2,8Ghz boost up to 3,98GHz | Noctua NH-D14 | Corsair Vengeance 12GB DDR3 2000MHz | Gigabyte Radeon 6990 4GB GDDR5 | OCZ Vertex 3 60GB SSD SATA3 | Western Digital Caviar Black 1TB SATA3 | Western Digital Caviar Green 1TB SATA2 | Corsair 850TX | Dell U2410

 

[hytecgowthaman]

If u r system (processor,gpu,smps)fan has any damage the system overheat quickly so protect from more damage the system shutdown without any error message like bluescreen message.
so check all fans are working correctly and clean the dust from cpu.
If problem in psu can do this.
try changing psu.
reset default settings in monitor.