mJust the other day I was PLAYING Counter-Strike 1.6 (Half-Life 1 Based Game) and my monitor started "flashing". Basically it will start getting really faded/white until it is completely white and then it while start quickly FADING back into color. This happens after about 4-5mins of being in game and continues to do so every few minutes.

Also if I alt-tab out of the game or exit the game the SCREEN flashes oddly with a very light/neon green color for about 3/4 of a sec and then resumes to normal.

I though maybe heat was the issue since I haven't cleaned out my comp in a while so I dusted it completely and still the same result.

Specs are as follows

NEC Accusync 95F monitor
Intel P4 2.53ghz CPU
Asus P4T533-C mobo
512mb of RDRAM(1066)
Two 80G Maxtor 7200RPM (8MB Cache)
Geforce FX 5600 256mb
SB Audigy 2
How old is your monitor?  You never know, it may just be on its way to its deathbed...and/or does not support the resolution and refresh rate that you are running.I say DEATH bed, My brothers is green now while he plays C.S
its still got a little bit of life in it!strangely enough changing drivers fixed it...seems to come back every 4 or 5 days though...then I just uninstall and reinstall the same drivers and it works again.