Random crashes in idle / web browsing

I built my computer about 8 months ago, it was my first build. Everything has been running fine until about 5/6 days ago. My specs are as follows:
ASRock 990FX Extreme3 mobo
AMD-FX 4100 w/ stock fan
MSi Cyclone GTX 550 Ti
WD 320GB 7200RPM 6Gbps HD
4x4GB Corsair Vengeance 1600MHz RAM
Corsair HX750 Modular PSU
Rosewill RNX-N300 Wireless Adapter
Rosewill Challenger Mid tower
Acer S200HL 20" LED monitor if it matters.

So a few days ago I got a pink screen in skyrim followed by an instant restart. I figured it was my graphics card right away. After that, I kept getting random hangs where my screen would go black, my monitor didn't detect video.


So, before doing any troubleshooting, I got a Sapphire Radeon 7770 GHz edition. It had the random hangs still, but I thought it was just the AMD drivers being buggy. It did the same thing where it wouldnt detect the input about 2 hours ago, so I took all RAM sticks out but the first one, and now it hasnt crashed yet. I'm on it currently and its running fine.

My question is, is this a problem with RAM, the mobo, or neither?