3 Monitors set to 144 Hz / GPU Overclocking Results In Computer Reboot

[iUnderclock]

Title pretty much says it all, I recently set all 3 of my monitors to 144 Hz and now any overclocking results in my computer completely shutting down then rebooting on it's own. I had my GTX 780 SLI set to about 1150 Mhz no problem but now i cannot OC one bit. Full specs below...

Specs:
Alienware Aurora R4
Windows 7 Ultimate 64 bit
Intel 4930k
Corsair 4 x 8gb 1866 Mhz 1.5v
NVIDIA GTX 780 (SLI)
NVIDIA GTX 780 (SLI)
Samsung 840 Pro SSD 256 GB
2TB HDD

 

[iUnderclock]

Ohh, btw, im only having this issue after gaming for atleast 30 mins, everything runs perfectly until it shuts down. No slow down, no lag at all prior to the PC shutting down.

 

[iUnderclock]

Even if you don't have a solution, can someone tell me if it's normal to have to adjust GPU overclock after switching from 60Hz to 144 Hz?

 

[iUnderclock]

PSU is a Dell W299G - 875 W