Black Plague Crashes Returning From Cells To Messhall

[nutcluster]

I've got the same problem - the following fix should work (I'm running an ATI HD 4650)

1. Go to the Catalyst Control Center
2. Go to 3D options
3. Disable Catalyst AI

The reason why this bug occurs is probably the Catalyst driver misinterpreting certain shader scripts, so disabling the 'AI' should make it work properly. While all the Penumbra games work just fine without the Catalyst AI turned on, you may find that it might cause major glitches in other games if disabled. Don't forget to turn it back on when you're done.

Note: Not a 100% guaranteed fix, but it worked for me.