Frame Rate choppy with high end system

[PerfectBlue]

Q9550 @ 3.0
4 gigs ram
GTX 280
Win 7

I have tried disabling multiple features such as SSAO, and switching the quality from high to medium, and even low yet this still persists. I made certain this problem was exclusive to this game by going back and playing Border Lands, Batman Arkham Asylum, Penumbra on high settings with no problems.

If it weren't for the choppiness in the frame rate, id estimate its at 50-60. But as it is, there is a brief pause every second or so that makes Daniels movement jerky. Switching the preset graphic conditions to low removes this problem entirely, I assume its SSAO and smoothing, because those are on for medium and high presets. I am running latest versions of Nvidia drivers.

ALSO, despite having shadows enabled, I do not see any being cast on objects when there is a light source.



Shouldnt this be able to run the game at medium or high presets?