@dbkdlk - I'm having the same problem, auto saving every turn, will let you play the next turn, but I find it freezes again within 3 turns.
Its started with SVN 671 I had played a high to low game till 1074 AD and had just been awarded my final civ when I updated and the freeze began.
Same problem, can't alt-tab, can't change active window, have to reboot the computer. Once I was able to change the window, and it showed the process in Zombie mode, so its crashed, but won't free up the process.
I've tried 2 different civs from a save just before the 3rd civ is awarded, and received a different civ as I hit the lead earlier, both were vassals of computer, and both have crashed.
I've looked at the Pythondebug.log, and it shows cities growing, but then freezes, no error.log
sorry, can't provide any more information.
Giagantic map, Marathon speed, random planet generator 0.68
I can play a number of turns as the 3rd civ, played over 40+ with 2nd till it crashed again at 1094 or so. 10 Yr's later then the Aztecs, who were the 1st Civ.