With a huge map, and at that late date in the game, you probably have loads of cities, your adversaries probably have loads of cities, and it is just possible that the save file has become so big that your computer can't handle it.
Have you tried reloading earlier autosaves and playing to the same date?
Cheers, --- Wheldrake
Have you tried reloading earlier autosaves and playing to the same date?
Cheers, --- Wheldrake