cjrgreen: You have an old CPU that is slower than the minimum requirement and has a small cache. The number of resources in the game is a killer for under-spec CPUs.
Since I have gotten better frame rate from lesser ATI cards (a 5670 doing 30 fps), do not blame ATI.
hulahula32: It's not blaming. It's straight from the horse's mouth. It is an AMD issue, FYI there is no ATi, no one works for ATi any longer. And again yes it's a known AMD issue and AMD has admitted and recognized the issue. They have been rushing past week to even provide a hotfix driver for both single and dual gpu users.
So yes, you're wrong.
Then why is my rig with a faster CPU (Wolfdale E6300, 3.33 GHz vs. the OP's Conroe E6400, stock clock 2.13 GHz) and lesser GPU getting better frame rate? At 1680x1050, high settings except for the usual turn-downs.
I agree, there are problems with the AMD drivers, AMD is working on them, and the OP should wait for the game patch and the hotfix before doing anything else.
What they are not, is they are not crippling problems, not indications that the game was optimized specifically for nVidia (have you been reading the complaints from nVidia users, or just ignoring everything that does not fit your preconceived notion that this is an AMD-only issue), and I do not believe they are solely or even mostly responsible for the OP's low frame rate.
Frame rate that doesn't vary with graphics settings or resolution sounds like CPU limiting.