Firaxis published a big patch to Civilization V today! It has got a long list of changes, including improvements to the Economic Overview screen, worker fixes and improvements, listing the cities that lack the buildings required for a given national wonder, and selling obsolete buildings to save on maintenance costs. There are also several AI improvements, a few multiplayer improvements and other miscellaneous fixes. :) If you don't have the update yet, it is automatically downloaded and installed once you launch Steam the next time.