I have the same problem as Mindful_Viking.
Purchased the Crusade DLC, installed it. While it was installing Microsoft VC, the job just hung.
Tried again, it says it succeeded.
Run GalCiv3, got the "choose a game" menu, pick GalCiv3, window disappears, disk churns a bit, then NOTHING.
No game, no windows with error messages, nothing.
Uninstalled GalCiv3 completely, rebooted, complete re-install.
Same result. NOTHING.
Any ideas, because I'm getting pretty frustrated. Can't play GalCiv3 at all now. Crusade has broken it.