PC stopped booting up. Should I suspect the mobo, the PSU, the UPS?

[solid_shepard]

So I built the PC in July and, despite an issue with the GPU (not the integrated one), it ran perfectly until just today. I left it on while I went and played a game elsewhere, and returned to see that it had shut itself down. Pushing the power button has no effect, except that I hear a tiny little noise somewhere in there. The motherboard seems to be receiving power because the lights that show the manual reset and power buttons are still lit. They're not working though. Any ideas about where I should start?

System Specs:

Intel i7 2600k
Asus P8Z68-V Pro motherboard
OCZ Elitexstream 1000W power supply
EVGA Geforce GTX 570HD GPU
WD 2TB HD WD2002FAEX
and if I'm not mistaken... Kingston KHX1600C9D3K2/8GX (2x4GB)

Power is plugged into a UPS:
Tripplite Omnivs 1000VA
It seems to be working for anything else that plugs into it.

 

[solid_shepard]

Best answer selected by solid_shepard.

 

[solid_shepard]

Yup, that was it. Now when I test the PSU, the light on the back is turning red instead of green.

 

[Mousemonkey]

This topic has been closed by Mousemonkey