I'm playing the vikings and I have currency researched. However, for some reason I get not gold in my cities from the tiles that produce gold. The thing says 0% of (say 20 for a city that has 20 gold), and I get 0 per turn. The only way it seems to get gold at all is to either have specialists or have the city produce gold. No gold comes from the tiles at all, and my economy is sitting on -19. Is this a glitch? Do I need a patch?