Colormap flash during age of Conquerors

After several minutes of playing Age of Conquerors, the
games suffers from what appears to be a "colormap
flash." The crisp, sharp colors of trees, lakes and some
other units are replaced with fuzzy, red and green
pixels. Military and village units and buildings are not
affected.

I have installed the lastest patches for AoE and verified
with the vendor that my video card is using the latest
driver. The colormap is annoying, especially to the eyes
but does not affect the game. No other games, including
Age of Mythology, are affected.

I am running on a PC, using XP/Home, 512MB memory, 32 MB
NVidia graphcs card.

Any help is appeciated.