Pregaming

Okay, so I have begun some preliminary fucking around with the map and the units and build/research order, and I continually get error messages from windows telling me that an illegal action has been performed and that windows must shut down Civ IV. Ummm....I have lost like 2 hours of game play! Anybody else have temporarily map freezes in which the map breaks down to only fog of war and terrain (sometimes roads) and then 8 or 10 seconds later it resorts back to regular game play?