Had a game just today where I was running around without building cities, pretty hard on the ridiculous difficulty setting but I found 1 bug.

If I try to attack a monster in my turn (pretty quickly after gaining turn) and the AI decided to attack the same monster, the game will move the AI to the monster, have the AI win over the monster (In this case) and the game would then "freeze" up, I was still able to move my mouse, view the unit details, but I could not move either of my units (Neither could auto-explore), I could not end the turn, all that helped was to reload the auto-save.

I had forgotten to turn on my screen-fraps program so there is no video showing me being frustrated

Sincerely
~ Kongdej