Hello,Do you know if you did something to get your last map locked again? It's the first time I read this kind of issue.Check if you can play it even if you have the word "LOCKED" on it.Regards.

Originally posted by Clockwork Orange: If the save file works on the other machine you can try manually copy and pasting the save from the other PC to your main and see if it works. Maybe the steam cloud corrupted.

I agree with @Clockwork Orange. Usually Steam cloud mades some problems with the saved games trying to synchronise.Try what this man sayd.Regards