Video Problem - Flickering/Pattern appears on Monitor

[purecomedy]

On a computer about 4 years old I've got am XFX GeForce 7900 GT video card and a 24" Viewsonic monitor (model is something like vm2433). In windows XP I would open games (the start menu is fine) but a few seconds into most games this odd grid pattern would appear on the whole screen. My solution was to alt-tab back to desktop and click back in and it would work fine. Minor nuisance.

Now I installed Windows 7 on this machine (heh, hoping to solve another problem) and now this video problem is 10x worse. It happens on Win 7 boot up, it happens right when I open a web browser, it happens randomly now and then. It always seems to go away after about 30 seconds. When I try to run Far Cry 2 though the pattern and flickering NEVER goes away is unplayable.

I've Tried:
-a few different NVIDIA drivers and the default windows driver
-I've tried messing with refresh rate, 59 hz and 60 Hz only logical ones really. I could do 30 Hz interlaced but seems stupid to try

My questions:
1. Anything else you recommend that I try? I've done some google searches and it seems like this monitor is notorious for some of these problems. Thing is I run a newer Dell machine on the same monitor and no random issues. I don't game on that machine so I can't confirm much there but plan to try a few games on it to see how it goes.

I'm considering trying another video card instead of that 7900 to see if I can get things working.