This has been a problem since i built the PC a couple of months ago,sometimes it does not happen for like weeks and sometimes several times a day: The Monitor goes BLACK and it says NO SIGNAL, I can hear the sound but i can not interact with the PC, when i open the case the GRAPHIC CARD FANS STOPPED SPINNING but every other fan is still on. Its not a cooling problem, the cards has 3 fans and have good temperatures. The power supply is more than enough top support my card. I have updated drivers.All the cables are connected properly.
However Depending on the quality of the protection circuits inside the PSU if a +12v rail fails it may just cut power to that rail and not the entire PSU.
So the only way to really test this theory is to either get the PSU tested under full load or instal a different PSU in the machine and see if it does the same thing.
Is this your PSU? [CORSAIR 550w Enthusiast Series CMPSU-550VX]
That PSU pushes 41 amps on the +12v rail and is more than enough for that Graphics card, but that doesnt mean the PSU isnt defective from the factory.
You wont know for sure which piece of hardware is at fault untill you do the trouble shooting to find out.