Can you not re-install without re-downloading the game? I have not used Steam, but I can't see not being able to backup a game, even if you have to be online to install it, etc.
I don't know if this will help, but Mehale in the
Never ending loading screen. 100% of the time topic posted a link for a
save game just after the intro. Presumably the game has maintained backward compatability even if there were changes to the save game format, so perhaps this save could help narrow down the problem.
