Poor Crysis Performance...?

I'm having some trouble running Crysis on any settings at any decent frame-rate for whatever reason. The game has been updated to 1.21, I'm running Catalyst 8.8 drivers, and Vista is updated as well. But, even when i turn the resolution down and set everything to medium (which looks horrible IMO) I'm only averaging around 20FPS and during hard action it drops to 15FPS. My system spec's are:

Intel C2D E8400 OC'ed at 3.7 GHz
4GB DDR2 800 RAM
2 x ATI Radeon HD 4870 in CrossFire
Asus P5K-E Mobo
Vista Ultimate x64

I understand that the P35 chipset is going to limit my performance in CrossFire for the second card but even a single 4870 should be able to run the game on High at a decent resolution with moderate FPS right?

I've tried searching the forum and opther forums online but couldn't find any information that really "matched" what I was experiencing.

Thanks guys!

I would say make sure you have all your Vista updates but you said you do.

I had that problem on a fresh install and was getting 10-20 fps on my 9950 and 4870 setup. Installed all available Vista updates and cruising above 30 fps (very smooth actually) with some very high and rest high settings.