A less obvious but known cause is a conflict with your router's Universal Plug and Play (UPnP) feature. Developers at Activision identified this as a possible workaround for the error.

Call of Duty: Advanced Warfare is a popular first-person shooter game developed by Sledgehammer Games and published by Activision. However, some players have reported encountering a frustrating error, known as the "5MB Error," which prevents them from playing the game. This feature aims to provide a comprehensive solution to fix the 5MB error in Call of Duty: Advanced Warfare.

Turn regular Shader Preload for general gameplay to prevent mid-match stuttering.