Screen dims when light sources go offscreen

[zool]

When I have a light source on screen, the game looks as it should. If I turn around the moment the light source goes off screen it emits no light. I tried to record a video of this using Fraps, but in the video the dimming doesn't happen.

I've seen a few threads about this issue, and I've tried everything I've seen suggested.

I'm using Windows 7 64bit, and an ATI HD5770 with the current drivers. I'm running the Steam version of Amnesia, so it's definitely up to date.

I've tried disabling Aero, unchecking every box in the graphics options, and running in windowed mode, nothing has had any effect.