thief deadly shadows running like a dog, is this normal?

[Reaper 392]

i would have thought that my computer would laugh in the face of thief deadly shadows, seeing that it can get ~30FPS in crysis when its maxed. however, im only getting 40-50 FPS in thief, despite its rediculously low requirements. also, during every loading phase without a loading screen (attempting to turn a page in a book and pausing the game are the ones that come to mind) the game goes incredibly slowly, in the example of the book, it will play the page turning sound effect 4 or 5 times before the animation is complete.

does anyone know of any way of fixing this, because im sure its a problem, and not my computer being incapable of running a 7 year old game