Hi Zak, thanks for helping. Your suggestion about older drivers was spot on. I'd been using 197.13, and also updated to 197.45. After I saw your post I installed an old set I had on my hard drive (169.21) and there was a definite improvement.
I still got a few freezes but they only lasted a few seconds, as opposed to hanging the machine so bad that I had to reboot. Most interesting was the fact that all of the freezes happened in exactly one spot on the map (the hill between the cities in the western most part of the revealed map just before the demo ends). Plus, it froze every single time I moved the camera back over that spot. After about a dozen passes the game crashed with this message: "GK2Exception - an error occurred while attempting to draw the screen"
I'll email the dump file from the crash and try running the game a bit longer when I have more time to see if there are any more freezes.
EDIT: After starting a new game from the beginning and playing for about half an hour I had 1 CTD, and 1 freeze that I had to reboot to get out of, which is an improvement over the way it was with the newer drivers.