Computer turning on, 3 seconds later off?

[ifreakyftw]

Yo guys! I've got my new ocz zx1250w psu today, and had a problem with the pc first running fine, ect. Then I turn off my computer and try to restart it, it starts but then shuts off about 3 seconds after! I've had this same problem with my coolermaster. Gx-lite 700w psu, it started occuring after I had re-applied thermalpaste to my HD 6950! This is doing my head in now, because this PSU doesn't let me discharge my computer, I plug it out, press the power button and let it discharge, but when I plug it it the computer starts, and everything happens all over again. Someone help me would be appreciated

 

[dannoddd]

Check whether your power switch is sticking.
Easiest way is to unplug the power switch header from the board and then turn it on by jumping the pins together with the tip of a screwdriver. If your board has a button then use that to turn it on while the power switch is disconnected.

 

[Novuake]

It definitely heating up... I would suggest starting it without the GPU to confirm. If the same issue occurs, reapply thermal paste to the GPU properly...

 

[ifreakyftw]

Same issues, I have a crosshair v formula.

 

[ifreakyftw]

Nono! The computer runs completely fine when it does start up (old psu). The gpu doesn't reach 70c, and my cpu (phenom x6) barely gets to 50c. I've double checked all the connectors aswell!