Sapphitre Radeon X700 blank screen

[pull81]

I have a problem with my radeon X700 - very often when switchin between resolutions (i.e returning from game to windows or loading a level in game) my screen goes blank and monitor displays information that there's no signal :\ sometimes ALT-TAB and switching between applications helps but mostly i have to shutdown my PC (reset sometimes doesnt help)
I tried all available drivers including omega drivers.This hardware is brand new .

My configuration:

Sempron 3000+ 64 bit
ASUS k84n-e DELUXE PCI-E
SAPPHIRE RADEON X700
SAMSUNG 710T DVI
Chieftec 360 W
WINDOWS XP PROF.

ANY TIPS?