One other thing that will cause a crash in STW (a bug I documented some time ago) was in the MI version. If you assigned an assassin to kill someone, and the target got killed before your assassin reached him (like if you sent 2 after the same guy), you could have a crash if you moved the assassin on the following turn. He would still show to be on assignment... Leaving him alone for a turn would clear his assignment queue. I believe this caused an instantaneous crash though, not an end of season/turn crash. So you might have to consider what your agents are doing as well.