jade empire not working

when i am playing jade empire after sometime when i am opening the town door to get weapons a error appears and the game shuts.


An Assertion failed in .\ccreatureappearance.cpp
line no 354
programmer says : CCreatureAppearence::CreatBodyAppearence () Model not found c_Chick

is the problem with game files or my system

i have core 2 duo 4600
512 ram
256 gforce 7300 le