I haven't seen this anywhere else on this forum, so I apologise if I am delivering news that has already been posted:

If you are playing a hotseat game, and any of the players has kingdoms installed, all other hotseat players need to install update 1.3 (or buy kingdoms) or the hotseat mode will no longer load properly.

I just thought I let you guys know, before you get a nervous breakdown like me yesterday, trying to find out what the hell is wrong with your game.