Using the 'Choose Religion' option. Researched Meditation first, chose Taoism and got the zoom in and window, chose to revolt to Taoism from the popup prompt, then total lockup as the screen began to unzoom and move to my active Warrior.

I mean total lockup. Couldn't ctrl-alt-del or even toggle any lock keys (caps etc.). Just had a frozen view of partially unzoomed terrain.

Had to hard boot to get out.

Intel core 2 duo 2.4 gig, GeForce 8800 GTS 640 MB (158.45 beta driver), 4 gig ram, Vista Premium.

Have you downloaded the latest BtS patch from the in-game Options menu ?
3.02 or something, a fix for a lock-up is in apparently:

I checked the SDK, and it includes 3 bugfixes as far as i see..
one for paratroopers entering a city only defended by planes, one crash bug fix, and a fix for a game lockup

No fix for that lockup I think.. the lockup fix I saw is one where AIs just never end their turn (but game responds well still)

This bug sounds like the graphics card driver locked up

Alright, my bad. It still is a good idea to patch anyway ;)

The heat might be responsible for a hardware lockup if your drivers are up to date, I noticed that Civ4 was pretty heavy to handle for my graphics card.
Untill I took the quality to medium-low, I would eventually run into a hard freeze.

Even with a new case with better airflow, I had to speed up the added fans in order to keep the CPUs cool with my first BtS game.

So update your drivers, turn down the graphics quality in the game menu or even the resolution and see if the computer still freezes.

Is it reproduceable from the autosave? If so, then please post the autosave here, along with instructions on how to reproduce the lock-up.