I am not sure of the correct expression for an instant power off (as if the plug was pulled from the wall): power off, or power disruption? Since a short time, if I leave the computer on during the night I find it off in the morning. Now also, while working, the pc just was shut down instantly. No reboot, no BSOD. Just instant OFF. Interestingly, after this happens, the power ON button on the case does NOT WORK. I have to turn the PSU off, wait until the on-board LEDs are off (discharged mobo), turn PSU on, and then I can use the power on button again. My Asus mobo BIOS has a Oversurge protection that can turn the pc off if needed for protection, but this does not explain the power on button behavior. Right now when it happened I was writing a Word document and the processor was idling at 1600. My PSU is Corsair HX750W My 3770K is overclocked to a turbo speed of 4800 Mhz. It seems PSU issue to me, but during heavy gaming I have never experienced this problem. Heat or wattage are not the problem, apparently. I am no electricity expert, so I would appreciate your help.