Very weird - cities and terrain improvements show up RED?

[Galumphus]

Specs:

1 GHz Athlon Processor (below recommended, but still, the game plays fine)
GeForce 6200
768 MB RAM

Here's the problem. Anything which 'sits' on the terrain (cities and terrain improvements, primarily, but also some units) are RED. I've attached a screenshot which can explain better than I could hope to with words.

If anyone has any ideas on how I can solve this, I would appreciate it very much. Note than when I dropped in my old GeForce2 in place of the GeForce 6200, the terrain goes back to normal (though the game slows wayyy down, of course)

[Galumphus]

I guess I should say, the game is still playable for sure, but I am having a real hard time telling things apart, since they all look red. LOL!

[Galumphus]

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