then it might be corrupt files of the game, reinstalling should fix it.
happens from time to time
btw: you can rar your installed folders so you do not need to run through all the install stuff.
the only thing you need to install it are some dll files (iff i remember right its two)
iff you want i can send you the stuff so you can rar it up and add a simple "quickinstaller" aka batch file

thats what i did, as i am sick of installing games over and over again.