I had catalyst 11.5 and hotfix 11.5a installed. In single player I had major issues. Very sluggish, huge stuttering, virtually unplayable. Even on the lowest resolution setting and lowest graphics options possible in game and in catalyst.
I’m using a Radeon 4850x2.
Rolled back to 11.4 catalyst drivers. Single player and multi now run without a hitch.
I recommend all ati users try out 11.4 .
Also here’s a guide to installing gfx drivers: http://www.techpowerup.com/forums/showthread.php?t=52502
If you happen to receive an error upon installing the video driver
“INF File Not Found”
Go to device manager > Under display adapter right click your video card > Update drivers > browse my computer > and select the ati folder on your OS drive (usually local C)
Hope that helps anyone having ati issues and no this will not fix server lag.