Auto black screen

Hello, I just built my friend a new pc, amd x2 6000+ 2 gigs of gskill ram ddr2 800. And a gigabyte motherboard. It has a Samsung syncmaster 906bw.

The problem is every time i play a game the screen automatically turns black, then the power on the monitor like were the power button is keeps beeping, like going on and off. Like it’s in standby. Now the computer doesn’t seem to be like shutting off everything is going just you can do anything with the black screen. I have system standby and never. And these happens randomly but occasionally

Please help


Which gfx card, and which PSU?

Seems as if the VGA sends wrong parameters about resolution, refresh rate etc. to the monitor.