Red pseudo-force-field over cities

[lusty_mike]

I have a display problem with Civ IV that doesn't seem to have come up in the forum yet where certain cities on the map acquire a red-coloured semi-spherical shape over them (bit like a force field), obscuring the city from view. It happens in every game, almost always to the capital city (by turn # 20 or thereabouts), and later to perhaps one or two other of my cities (never to any other civs). The shape also forms over animal enclosures, but nowhere else. This problem has persisted even after the installation of v1.09 patch (which did fix display issues with seeing construction thumbnails in city view mode).
Is this a problem shared by anyone else?

 

[The Condor]

Do you have a screenshot? Read the first page of the bug report forums to find out how to make them. It would help determine your weird glitch thing.