This city is only producing 1 hammer, yet it shows 12. After I process the turn it corrects. The screen also shows that the yield display is not working in the city screen either. My video card is GeForce4 MX 420 with the latest driver.
101823

Did you just chop a forest or something? Another poster reported the same thing but it was because they chopped a forest (ie the game is correct)

The problem is not in the city display. I think there is a bug whereby the terrain only shows toast (food) and doesn't show hammers (shields) So all those squares with 2 toasts, if you drag your mouse over them you will actually see that many have hammers in them. To recape, the 12 hammers are being shown in the city screen but are not appearing on the terrain. I hope others can confirm this.

see here: http://forums.civfanatics.com/showthread.php?t=134046