And I figured it out.. as mentioned in another post. Units on Auto-Explore often get stuck and cannot complete their turn. Simply move them to complete their movement.. then take them OFF Auto. This is a bit odd, since the units are in open space. Still, it beats not being able to advance.
Ok, here is how I solved the problem for me. See if you have any units doing "Auto Explore" If so, stop them. As soon as I found and gave an order to the unit on Auto, it went to the space I picked, and the turn advanced. For grins, I have duplicted the problem several times and can confirm it happens regularly to me when one or more units are auto-exploring. Please post back if this helps at all.
ok further testing shows that something bad is happening at Turn 800. The game slows down and turns are no longer possible. I will keep adding info as I can until I am completely out of patience and give up. If anyone feels a save game (or two) or other info will help I will find a way to post it.
Happening to me too right now. Let us compare notes. What turn #? How many cities do you have? What was the battle after which it stopped?
I cannot advance the turn past 804. It may have nothing to with "Turn 804" but it happens right after I establish the crystal mine where I have to mine 25 crystal. Returning to previous saves is only good until I reach that stage of the game.