The version will be on the start screen, OK your Campaign.txt file is already been deleted and is running from a internal copy do to the producer of the game's CD.
It's possible that it could be another problem: if you installed the game, ran and saved the game, then updated it, it could of messed up your current game. Try restarting your game with a new save and see if you can buy and sell things.
I wish you luck man.