Instructions
Exit the game through the game's menu. Abruptly shutting off your machine or closing the program through any other means can close the program in the middle of creating a new save file. If you stop this process, your save file becomes corrupted.
Upgrade the drivers on your video cards. Video card manufacturers often release updates for products in the form of drivers. These increase the efficiency and stability of the product further minimizing the chance that your game will crash in the middle of creating a saved game file.
Download any available patches for "Modern Warfare II." Whenever you launch the game through the Steam platform, which is required to play the game online, it automatically download and install any necessary updates. Many of these patches increase stability and take measures to prevent saved data corruption.