Graphics Glitch on Black Plague

[juliantcf]

Hey forum, after a bit of troubleshooting, driver updating, and patching, I've decided to post here. When I start up Penumbra: Black Plague through Steam (where I purchased it) it runs fine, but there are some quite annoying graphical errors. Depending on where I stand/look, parts of the screen will turn black. As an example, in the very first room the game starts you in, I look over at the pipes near the door, and various things turn black. The walls, the mattress, parts of the floor, stuff like that. I've gone past the first loading screen and the problem still persists when I look at various areas. I downloaded the patch for it, but the problem still persists. I have an AMD Athlon II X2 245 @ 2.90 GHz, 10 gigs of RAM, and built into the processor there's an ATI Radeon HD 4200 graphics card. Not the greatest rig, but I'm able to play Overture and Amnesia: TDD with ease at a low resolution. The patch for Black Plague is supposed to fix these problems with ATI cards, but it didn't for me. Any ideas?