devland: It doesn't happen to me.
The game does hang from time to time while loading new assets, but only for a fraction of a second.
(there is no known fix but check out this article for more info:
[url=http://pcgamingwiki.com/wiki/S.T.A.L.K.E.R.:_Call_of_Pripyat]http://pcgamingwiki.com/wiki/S.T.A.L.K.E.R.:_Call_of_Pripyat[/url]
the part with the 4GB memory tweak might help)
Your situation could be explained by poor HDD performance such as having other programs doing HDD intensive tasks like downloading or copying files.
I thought about the HDD load, and tried closing all other programs before running. It didn't help. I've tried the game on my older desktop, and the error is not present there, resulting in a much better gaming experience.
Desktop specs:
Windows 8.1
AMD Phenom II X4, 3.6 GHz
4 GB ram
AMD Radeon HD 6870