In the late renaissance I am getting a significant pause happening in the graphics at the beginning of a turn. I thought it was due to one of the new platyping wonders so removed the wonder. It helped but I a still getting the "lock". It appears that BtS has stopped or hung but wait long enough and it comes back fine. It is particularly noticeable when the diplomacy screen opens since you can't select any option.
Platyping? Was the Cyrus Cylinder one of these? I'd just spent ages building it in my current game and now it's gone
