Dell LCD + game = black outs!

I have a dell E151FP LCD and whenever i use it for playing games it'll play and then after awhile it'll blackout like its in sleep mode then come back on, though the game doesn't crash. It works fine in anything else but in games it does it.
The two where its most pronounced is Half-Life 2, GTA: SA and The Bard's Tale, i have yet to test it with anything else, but this is only a recent problem. System specs as posted:

Dell E151FP [Monitor] (15.2"vis, September 2002)
ATi Radeon 9600XT 256mb AGP 8x
Creative Labs SB Live! 5.1
AOpen Springdale-PE 918AT10701
Pentium 4 2.8 GHz
1gb Geil Dual Channel (2x512) PC3200

This is a recent problem (5 days now) and it has never happened before.
The hardware specs haven't changed in almost 3 months, and i tried it with a GeForce 4 Ti4200 126mb and it had the same effect. When i tried it with a different monitor it worked fine any thoughts?

 

Quick note, its not just one game, its all games. Even Half-Life 1, Please help!