At the start of the turn a dialogue appears asking you to choose which immigrant will appear at the docks (the option which you get with a founding father). Once you have selected one the game freezes. I'm fairly certain that this is the cause of the crash as I have tried to change as many other things as possible and the crash still occurs. I have saved the game a turn before the crash. Hope it helps. Good work by the way the game has come a long way since version 0.4.
Savegame a turn before crash