I had this problem. Reported it to 2K Greg during the beta with zero response, and it was still there when the production patch arrived.
I've fixed it, thanks to inspired advice from Gyathaar. I edited the cofig.ini file in MyGames\Civ5. Changed one line to:
EnableGameCoreThreading = 0
My problem was that I run the Windows version in a Parallels WinXP virtual machine on my Mac, and I only gave Windows a single core to play with. Apparently, the min specs for this version require Dual Core?
[PS] Gyathaar credits dshirk's post #224 above for this solution.
Thanks, I did that earlier today and it fixed the problem... I would be so lost without this forum lol.. Funny how that one number outta all the files in the game would have that big of affect on the game.. Im so glad that I can play the game again.. Thanks again for the help and info ..