Loss of DVI video/black screen

When playing Everquest (and so far, only when playing Everquest) my monitor after a while will simply lose the DVI signal and go black. No picture, but the game runs on in the background just fine. Sometimes takes a few hours, and once it happens trying to log back in results in the same problem only within minutes. Any ideas? Also, under the game options it shows the game as reading my old video card (was an Nvidia 7300 as opposed to the 9600 I am running now) and I have no idea how to change that setting to show as correct.