550W psu for p8p67 deluxe?

I just built my first pc, it has the aforementioned mobo, a nvidia geforce 280, a i5 2500k sandy bridge cpu. one blu ray drive whether that matters, or not and 8 gigs of corsair vengeance ram. the pc keeps freezing after about an hour of starting up. the ram tested ok and the cpu temp is fine. im not well veresed enough to trouble shoot and i think it may be the power supply. any ideas?

thanks,
Jeff

Can you tell me which operating system running? Also I wanted to whether any antivirus program installed on the system.
For time being I recommend that you should boot the computer into Safe mode. You should reboot the computer and Press F8 from the keyboard. After that select Safe mode from the Advanced Boot menu. Now see that the computer is freezing or not.