Unplayable FPS 1900x1200 Lowest, HD5850, 8GB, Win 7x64, Phenom IIx3, Demo was perfect

[defach]

I get totally unplayable FPS at 1900x1200 (native) regardless of the rest of the settings. This is amplified at the beginning of the office level (with the rain). I've followed most of the advice I could find in this forum (along with not being a computer novice to begin with), but I cannot resolve the issue. Here's more system info and what I have done:

Windows 7x64 ultimate
AMD Phenom x3 Black @ Stock
Radeon HD5850 1gb 9.12
8gb RAM
SB X-Fi Plat PCI
300GB + HD space free on a 1TB Caviar Black
KF = 0% fragmentation, overall < 5% (Diskeeper 2010)
Microsoft Security Essentials (Whitelisted steam directory)
Cache set to 256mb; I load the level in just a few seconds
Overheating is not a problem (verified HWmon)

At 640x480 windowed, the game has perfect FPS at low settings, but it is nowhere near where it should be on highest settings (I see a stutter). Mouse lag settings have no effect. For perspective, I play crysis at 1900x1200 on gamer settings at ~30fps. I was also able to run the KF demo a few weeks back (free weekend) at max settings without any trouble at all. This was on catalyst 9.10 (I think) and I'm unwilling to roll back unless a dev verifies that's the specific issue.

Please help. I can provide more info if necessary.

 

[Nitronumber9]

Well firstly your out of date driver wise, its 9.12 ATI cards are on.
Is there a possibility of something trying to lock into the game forcing it to slow down? (Fraps for example)

 

[Zetsumei]

are your actual fps low or does the game feel like its on low fps.

type in the console "stat fps" to see your actual fps amounts.

( the vidcard shouldnt be an issue generally, i got a 5850 as well on win7 64)

 

[Darkwraith]

I would verify the FPS as well, as you've only said it is unplayable. I play at 1920x1080 and see 50-60FPS, even with maxed settings (minus coronas) and 2X AA. For comparison, my system specs:

Windows XP (I know, its not 7)
AMD Athlon X2 4400+ @ 2.875 GHz
2GB PC6400 @ 950 MHz
Sapphire Radeon HD 4670 with only 512MB DDR3 and 9.12

I can't believe that running the game at a similar resolution with a more powerful system could run worse than my own setup. I've not run Windows 7 myself, but with the increase in hardware it should more than compensate.

 

[=GG= Mr Moe]

Wasn't the Demo the full version of the game???

 

[defach]

Well firstly your out of date driver wise, its 9.12 ATI cards are on.
Is there a possibility of something trying to lock into the game forcing it to slow down? (Fraps for example)

I am running 9.12. I do not have anything hooking in to the game like that. Steam overlay on/off makes no difference. Neither does windowed / fullscreen.

I used "stat fps", and at highest settings, I get 5 fps standing in the rain outside office. At lowest, I get 11-16. I know when it was the free weekend I was getting 50+ FPS (based on its buttery smoothness).

Yes, now that I remember the demo was the full game; I did uninstall it before I bought it on holiday sale.

Any more ideas?