Lighting Problem, weird colors

[WHiTeRaBBiT]

superluser, thanks for the video.
All, how much RAM does your video card have?
Have you tried lowering or disabling shadows to see if that fixes the flashing?

I think you hit the nail right on the head.
Turning shadow and/or SSAO resolution down prevents the problem more often, the lower the quality the less likely it will happen. I think its also dependent on each level and how much memory is being used overall, so a matter of balancing settings on average to work well through whole game. In my case I'm running Debian Sid on an GeForce 8800 640m and choose to keep shadow map resolution high and SSOA on medium. I've also had similar issues running Nexiuz/Xonotic and found turning down shadow resolution, texture resolution and anything else that consumes GPU memory will help.

Thanks Urkle