If you are experimenting with units mods (as undoubtedly most forum readers/posters are), you may find it important to copy your civ3mod.bic file with a particular saved game (i use winzip for this). Any heavy mods to the file after playing a game will render that saved game unloadable.
Any time i save a game, i zip it with the civ3mod.bic file i played it with.
Any time i save a game, i zip it with the civ3mod.bic file i played it with.