weird city screen bug

[sherbz]

I was playing a game as the khumer yesterday, and without further play testing i will not be able to verify it (to see whetehr its unique to that particular civ. I shouldnt think it matters but ive had the problem once before and im almost certain it was with the khumer). But pretty soon after i teched alphabet my capital was inaccessible. Well, i say it was inaccessible, when i double clicked on it i could move citizens around on their tiles, but there was no city screen, no build queue, no city info. It was like all of that was invisible. It also made the game crawl and any unit coming from my capital moved very very slowly. My other cities were fine. Any ideas?