I doubt this is a TET problem. Especially the way you describe it happenning only on specific turns.
If you've ever re-loaded the game to "correct" a certain battle-gone-wrong, you'll have noticed that the battles *always* go the same exact way, down to the number of HP lost. It seems Civ3 generates all the calculations for combat in advance, rather than generating them at the moment combat is initiated. So, if you're really observant, you can figure out which units to use when by trying a test run, then reloading it (thus defeating tanks with warriors sometimes :-\).
Anyhoo, my point is that I imagine Civ3 messed up somehow for that turn, and that is why the crash happens only on certain turns, and always on certain turns. You should report it to Firaxis -- they do have a suggestions form on their website. (Also good for suggesting stuff for Conquests.)