I just loaded up a new game of Avernum: EftP. As soon as the game starts, the graphics are glitchy: every few seconds a random tile will "light up" by displaying a grey or black square. It's a bit as if those ground tiles were flickering. I've tried changing the game area and resolution, that did not help.
I never had problems with Avernum on my machine before. I've had to change out the graphics card about two years ago, however, and I guess I haven't played it since then. I own the game on Steam, I'm running Windows 7 Home Premium (Service Pack 1). My graphics setup is as follows