Something extremely strange and apearently random

[Crushyerbones]

I was just about to run dow as usual and for no particular reason I notice there is a strange diagonal (is this how you spell it in english?) line on the top of my screen wich doesn't let me see the unit on the main menu and the menu itself, the background displays as normal as does the rest of the screen.

I haven't installed anything out of the ordinary between the last time I ran dow (besides Serious sam: TSE and Hostile waters), so what could cause this? It's extremely annoying as I can't see half my screen!

Edit: forget it, restarting worked :D