Alright so i have built a computer about a year ago, its been serving me very well since then, but only recently has it been turning off randomly. It happens if im playing games, or im surfing the web, or if the computer is just idling. It will shut down and wont turn on, and in order to turn it back on i would have to unplug the power cord and wait for an hour or two and then it would usually boot up just fine. I dont think its a PSU problem because when the computer turns off the motherboard light is still on. Also i checked CPU temps and they seem maybe a little high but still safe, it idles at around mid 40's to low fiftys, and under load it gets to about 80 degrees Celsius. Also i overclocked my CPU a week or so before this all happened if that makes a difference in anything. Any help will be greatly appreciated, thanks!
Specs: Intel core i7 920 OC'd to 3.16ghz
ATI Radeon 4870 1gb OC'd to 900mhz
750W Corsair PSU
6GB Corsair DDR3 RAM 1333mhz
1 Terabyte hard drive 7200 RPM 32mb cache
Antec 900 case
Update: i reduced all cpu and gpu clocks to the default clock speed and they now idle my cpu now idles at about 50 degrees Celsius while my gpu at 52 degrees Celsius, and now my computer is still shutting down randomly, i really need some help here guys, what is going on?