No! Not the HDR, that's what makes it all pretty-looking!
First off, i have read that a few people fixed this by lowering their resoloution to 800x600 (in game).
It doesn't appear to be artifacting, more like corrupt textures maybe?
Have a run through the 'Common Game Issues' thread in my signature if you haven't already. It could need a simple re-install.
Or, if you prefer, you can continue playing with sub-par graphics
.