I get black screen while playing the game. need help

[dasd23]

This is very annoying and i get only this problem on this game.

i play crysis without crashing or getting black screen.

but when i play the demo game on full settings i get black screen after a few seconds into the game.

is this a common problem or its just because of the demanding physx and buggy game?

I have Geforce 9800gtx+ 512mb. latest driver 185.85.

I dont get any black screen for other games.