This is something that's been going on since I started playing a few months ago. I'll be playing fine and then all of a sudden the screen will freeze for a few seconds and then the whole monitor goes dark. I can still hear the game running in the background. If I have another application running (even something small like the calculator) I can ALT-TAB to that other application and the video comes back on (I can also sometimes hit the "windows" button to counteract the video blackout...but rarely). However, if there's nothing else running, then I literally have to turn off the computer and re-boot in order to get the video back up and running.
I've tried playing W101 in a window, with different video settings, different resolutions, pretty much everything I can think of. But the problem always creeps back up. Strange thing is, this doesn't happen to me with any other game.