Game hangs on new turn

I run the game through Steam and have all the DLC.  Rarely have any trouble however this game save game that freezes locks up as soon as you press next turn.  I tried several combinations of restarting the game, reloading progressively older saves etc but it always stops after this turn.  Hoping there is a bug to be found and fixed here.  To be clear the game itself doesn't hang, I can go do diplomacy, view the tech tree etc but advancing to the next turn simply stops.