Computer is going into Hibernation / Sleep Mode while playing FFXIV

The past week my computer has been going into a sleep/ hibernation mode while running ffxiv this takes place withing 15min to 2hours of running the game and will not wake once this happens. This only happens while running ffxiv, i can leave my pc on continously on the desktop or browse the internet without problems. However, once in the game this will take place and the only way to exit the sleep/hibernation mode is to hold the restart button or turn off the pc. Ive read on different forums and seen people post who are experiencing very similar issues with different games. Ive tried several things like adjusting the power settings under the control panel, i turned sleep/ hibernation to "never", ive cleaned my computer insides thoroughly to remove all dust which may cause overheating ect. On a different forum it was thought to be a power supply unit so i went out yesterday and purchased a new one and ran FFXIV over night. the game stayed on for 11 hours and i thought i finally found the cultprit, then it did it again. i'm extreamly frustrated and now have two powersupplys if anyone has any suggestions or ideas of what may be causing this please help me. My pc is only 1 year old and shouldnt be having hardware issues ive provided my specs below. any help at all will be greatly appreciated thank you.

My Specs:
Windows 7 Ultimate 64 BIT
Tower: Cooler Master elite 310 ATX
Harddrive: ASUS M4A88TD-M - AM3- AMD 880G -DDR3- SATA 6Gb.s
Processor: AMD Phenom(tm)II X4 965 Processor 3.40 GHz
Ram: Corsair XMS3 4X 4Mb (16mb)
Video: Nvidia Geforce GTX 560 Ti
PSU: 850W Thermaltake Black Widow
Monitor: HP2311x 23"

Could it simply be overheating and doing some sort of "emergency poweroff"?
FFXIV is the only game that overheats the graphics card on my laptop even when it is under-clocked - again, at random times.
Try keeping an eye on the temperatures on your PC.

I had a lot of sleep/hibernation problems with w7 (for example when set to never sleep or hibrinate it would go into that mode when I left it over night). Try downloading insomniac. It keeps your comp from sleeping while it's open. Don't know the route problem but it's a fix.