PSU Problem(I think)

Alright, so just under a year ago I built my own computer. About a month or two ago, I got some weird problems. What would happen is around 7 o'clock at night, the computer would turn off. (This has only happened about 5 times, but it was annoying. Most of the time I wasn't there, but it did happen once when I was playing CSS) So anyway, my computer again turned off sometime after 7 o'clock at night, so I go and try to turn it back on. Turns out, it won't turn on! The case lights will come on for under a second, unless I hold the power button down, in which case they stay on for about a second. So I unplug everything vital, and try to boot up the computer using my Memtest86, and unsuprisingly it doesn't work, however I notice on the back of the PSU(this is my PSU(520w version): http://www.ocztechnology.com/products/power_management/... ) that not all of the LEDs are green when it powers up briefly. I take out the power supply, and using this guide, I attempt to measure the voltages. However, the same problem with the PSU not staying on is still present. So, here's the question: Is the PSU broken? If so, will OCZ replace it(as it should be under warrenty because it's less than a year old)/should I just ditch OCZ and get a new PSU?

I did a search but I didn't come across a similar problem, so if there is a topic sorry for double posting.