Locate your game directory and delete "cod.exe", once you do that it will download a new exe.
Steam:
(Drive your games saved on):\Program Files (x86)\Steam\steamapps\common\Call of Duty HQ
Battlenet:
(Drive your games saved on):\Program Files (x86)\Call of Duty\_retail_
Once done, proceed to scan and repair your game.
If you're still crashing, please make a ticket in our server.