I've posted this on other quessies. Here again, in case you didn't fix it.
Have you considered your AC supply to the computer? Have you added any multiplug power adapters lately, or cords.
First check this simple issue out out before going into depth with all sorts of other things with your rig. This issue drove me crazy for a while.
One thing to remember is that these bigger PSUs actually draw a lot more current on the AC side than smaller wattage ones.
So, if you have a thinnish little kettle plug cable to power your computer from a multi-adapter extension cord you will have voltage drops on the AC side, causing a droop in current flow to the computer. Also happpens with a low gauge power cable even if direct to wall receptacle.
These PSUs need over 12 Amps on the AC side. AC receptacles are rated for 15A, (leaving only 3A spare), so if you have other things plugged into the same circuit they could cause voltage fluctuations, and its worse if you don't realise someone else in the house could be turning things on and off on the same circuit: -- you know, like when your desk light dims because there's a whole lot of things plugged into a multi-adapter....
This can be enough to drop the PSU momentarily and cause your computer to bomb out leaving you wondering 'what the heck'. So make sure the AC power supply cable is, (1) a proper one that is rated for high current i.e. 14AWG wires in it, and (2) also just plug it directly into a wall socket or have it on its own decent extension cable to a receptacle.
Let us know how it goes.
Good luck.