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I had the same issue, but in campaign 5, and on version 1.3. I decided to look at the cheat codes and entered @win, and the same problem occurred as with you. Because of this problem, the campaign save was uninstalled to level 1, mission 1 of campaign 1, so there is nothing I can do to help. You'll have to start over, or get a campaign save from someone else.
You know, I didn't use any cheats... and having to play through it again... I've seen licensed games for 400 rubles, but I wouldn't want to play them 5 times... it's easier to pay 150... at least I wouldn't mind throwing it away.