I had the problem of the BLOOM effect completely make the game unplayable, and causing 70% graphical data corruption.
Upon finding, and reading this thread I played with the settings that people tried and it worked fine for me.
This is what I did.
Get ATI tray tools, I also have RivaTuner that I run 24/7
Riva tuner sets my GFX's to be under 50C under 100%load
I set the Vsync on always off, change the file quee to 3
Also added -winxp to command line.
set AI to Advanced and my performance boomed from 30FPS/AVG
to over 60FPS/AVG with all Setting on MAX.
This is what I run.
2x HD4850's
Dual Core @3.25GHZ super cooled to 25C
3GB DDR3