I have to admit that I have never seen anything like it.
It looks like a
openGL problem.
The command
r_fastsky set to
1 could maybe help you out(seta r_fastsky 1).
You can past text into the console by pressing the middle mouse button.
Link:
Introducing the game console
If nothing did help so far...
You might want to check for newer or older drivers for your graphics card, but make sure you de-install the current driver correctly.
Download first new drivers for your graphics card, if you have the latest drivers get some older drivers.