Ive been using the mac OS for over a year now on this hardware

Asus A8N-SLI
Nvidia 6600
AMD Athlon 3800+ X2
2 gigs ram

and these operating systems on separate hard drives with chameleon RC3
Leopard
Snow Leopard
Windows 7

For some reason however after about a month in I start experience a graphical glitch, it starts out slowly and then occurs so often it becomes annoying. First it will start whenever I play a video (on any media player or online). The screen will go black for a split second then go blue for a few seconds and then go back into the normal screen. This will constantly repeat itself every so often. However If I make the video window smaller it will some times alleviate this problem. After a while this will occur while i'm on the screen saver, while I use expose, while I use photoshop, when i move windows around quickly.

I use an EFI string to get my graphics working, I should also note that I also get the same problems in snow leopard however they occurred from the start and are much more frequent when using Quicktime X than other media players. The strange thing however is that I can play games without any trouble, accept when exiting the game then I sometimes have to go through around 5 minutes of this flashing If anyone could give me suggestions on how to alleviate this problem on leopard I would be very grateful and even more if you had a way to fix this on snow leopard as well.