Ok, this is down to an XML change SO made in rev 2529, where he deleted some apparently duplicated heroes. In your game one of these heroes (Babur) is the best land unit in existance (at the time) in the game (which is used to scale various things).
The load didn't cope with this state.
I have just pushed a DLL fix to SVN that will recalculate the best land unit for saves in that state on load. I have tested it with your save, which loads fine now (though some player has lost a hero!)