Display problem, lack of any video

[Eraser_tr]

I'm having a frustrating problem. The game starts up fine, but when I go to play any map/scenario the display just goes black and the monitor's power light turns on and off. I can hear the sound in the background and alt-tabbing out has windows and the game showing as running perfectly.

I played the demo of CotN a few months ago and it worked perfectly. I also reinstalled the original Arma and had the same problem, which also worked perfectly a few months ago.

It's obviously a video problem, but I can't find anyone else having it with either game.