The Save Game Could Not Be Loaded

Anyone know what causes this? Just tried to load a game and I got this message.

Your game is probably corrupt and unless you have the rolling save feature enabled then you'll probably have to start again. When you last used your computer was the game finished saving before you switched your computer off? This problem can happen if you switch off your computer prematurely. You should also make sure that you are fully patched but if you are using steam then this is done automatically so dont do it yourself or this can also cause problems.