I know nobody here wants to hear this (especially those with corrupt files), but you've GOT TO back up your leagues often -- and always before making any major changes to the league (such as adding minors). I always back up my leagues, at a minimum, on December 31 before advancing to the next year.
Simply copy the .lg folder to another location.
Then the worst that can happen is you have to repeat one season. Still frustrating, but much better than losing 40 of them.
Anyway ... sorry to be preachy. It seemed like a good opportunity, though.
CPAScott