GPU 3D Based Application Issues

Windows 7 Home Premium x64
Asus P5N-D Motherboard
Intel Core 2 Quad Q6600
4x 2GB Corsair DDRII
2x NVIDIA 9800GTX+ 512mb In SLI
Corsair 750Watt PSU

System temperatures run at (idle average):
CPU: 46oC
GPU: 37oC

I have had a number of issues recently with all kinds of 3D based applications (mostly games) on my PC. It seems to have started around the time I installed the most recent NVIDIA drivers (301.4) and following playtime on Skyrim.

I've since installed an older NVIDIA driver (296.10) and started my computer on a clean state but issues Persist. When my games get up and running I get issues such as the following:


But for the most part they will stutter, black screen and crash to desktop. When they have rarely got up and running there seems to be no issues for a while and then problems recur; including severe drops in performance.

I have had notices stating 'Display driver stopped responding and has recovered - Display Driver NVIDIA windows Kernel driver 296.10 stopped responding and has successfully recovered.'

Even the NVIDIA panel is having Issues lately.

I recently cleaned the machine, but took all necessary precautions as I have since I purchased it. I had also, until my recent system wipe, overclocked the cards, but did so with like wise precaution.

Any and all help would be greatly appreciated.