PC players have the most tools at their disposal to fix a "Call of Duty Black Ops 2 save file corrupted" error. Try these methods in order, from easiest to most advanced.
A common BO2 issue on Xbox is that Zombies stats appear corrupt but campaign is fine. This is often a server-side desync. Sign out of your profile, start the game as a guest, then sign back in during the main menu. This forces a stat re-authentication. call of duty black ops 2 save file corrupted