For the past week or so, all OpenGL Programs on my PC have started flickering. Including HL. 
By flickering, I mean the screen switches between the image, and complete white-ness at the same refresh rate as the program runs at. It does this forever and will only stop if I [ALT+TAB] out of the app, and back in again. And it also happens only in Full Screen mode. It doesn't happen if I run the programs in Windowed mode.
I've tried fiddling with the VSync settings, the FSAA settings and the Page Flipping but I can't solve this. Does anyone know how to fix the damn thing? I cant find anything on the interweb, and nothing on NVIDIA's site either.
I'm running on a P4, 2.4Ghz with a GF4 MX 440 and WinXP Professional. Also, in the case of HL alone, when I exit the game, it crashes with an error in "nvoglnt.dll".
If anyone could point me in the right direction for a fix, I'd be much obliged. (God this problem is annoying
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