Low FPS

Hello All

I have just went and purchased the game + DLC off steam.

i was playing fine, up until the part in the beginning

Spoiler

escaping from being captured, where you see your friend in jail and are crawling through the vents to find and save him

and all of the sudden i dipped down to under 10 fps.

have gone through all the update stuff to get rid of the flickering shadow issue I was having which is gone, but I now it's not playable.
I even lowered graphics / turned settings down, and it still is under 10, something else must be causing it?

My Specs are as follows.

Code:

Windows 8 
8 gigs of memory
256gig solid state.
AMD 7970 gpu
intel i5 ivy bridge