Random black screen shutdowns

[xBLiNG]

So I upgraded from a 5770 to the 290 windforce in the rig in my sig not to long ago, and started experiencing issues, the system will hang for a few seconds, then black screen and restart, I have made sure that I cleared all the drivers from my old card, but that didn't help.

Next I thought it was the PSU, however it wasn't happening when gaming or doing anything stressful.

The PSU then died, so I replaced it with a SuperFlower 550w, recommended by many on here, and assumed that was the issue all along, however upon installing the new PSU, I have just had it happen again.

In event viewer, I see two things I think might be it:

A fatal hardware error has occurred.
Component: AMD Northbridge
Error Source: Machine Check Exception
Error Type: HyperTransport Watchdog Timeout Error
Processor ID: 0

and

The computer has rebooted from a bugcheck. The bugcheck was: 0x00000124 (0x0000000000000000, 0xfffffa80073368f8, 0x0000000000000000, 0x0000000000000000).

I have tried a sfc /scannow, and it found nothing.

Does this mean the NB on my mobo is dying? Or could it be something else? Neither the CPU or GPU are OCd, and their temps are fine (CPU 34c, GPU 42c) at idle.

Any help is appreciated.

 

[xBLiNG]

Bumping this, still getting the problem, GPU and Chipset drivers are up to date.