That is a classic MTW save file corruption. Sorry, you will have to restart the campaign. MTW will eventually corrupt (as will STW and RTW.) Fortunately, it is easy to avoid with a bit of discipline. Save the game at the start of each turn before moving anything. I have never had a corruption when following this simple rule (took me awhile to figure it out--the hard way.) Corruptions come from saving late in the turn or at the end of the turn. Ironically, "Autosave" is at the end of the turn. That makes "Autosave" more prone to corruption.

Eventually you have to go back and delete some saves (the game only allows 100.)