I got the steam version, can't rename the executable.
I was getting same problem with my 4870x2 card, with crossfire enabled and latest ATI drivers. I ran multiple test without any good result until I downloaded "Radeon Pro" at http://www.radeonpro.info
I made a new profile with my crisis 2 game, I've check in advanced Catalyst AI and set it to "normal". After it's done, go into Tweaks tab and force que CrossFireX Profile to Bioshock. Apply your settings by right clicking though your Crysis 2 profile. You can set some other tweaks by auto-disabling Aero and always forcing v-sync off, it help a lot on FPS aswell.
Launch the game by right clicking on your profile. Enjoy your CrossFire enabled and fully functionnal.

I was running at 44 average fps with miminum "high" setting and now i'm able to play on extreme settings at average 75fps.
Okay so I'm a super-newb at these things, I did install the application and added Crysis 2.exe as a new profile, and also forced the Crossfire thingy to Bioshock....
... But I can't find the option for the AI in the advanced-tab! Hell, I can't even find it anywhere! Where is it supposed to be?
Thanks.
