Personally I would verify your game cache via Steam, as I am assuming that your are on PC.
Verifying your game cache will removed any mods you have installed (which may have caused the problem), and it will automatically download any broken, missing or modified files from Steam. This will leave you with a standard fully patched game.
You will not lose your career game save when you do this.
If you don't know how to do this, have a look at my stick post here :-