During the Final Crysis 2 released I played it on Extreme settings for PC i get about 35+ FPS there is some point in multiplayer but mostly in single player when i look at some parts of the map or a direction of something it looks so choppy, but i am still getting a great FPS, the rest is very smooth and fine just there is some parts i look at during gameplay it looks so choppy. is this a normal bug or something or a computer issue?

Specs:

Ati Radeon HD 5770
Intel Core i7 870 Quad Core 2.93 GHZ
8GB of RAM

Thanks for the help.