Did you save it after you exited out of the campaign.That is what I always do is save it even though it autosave it best to do this.I learned from my Trek games to do this as well when in a campaign.I am not sure as to why you are crashing it may be your memory or vid card.How do you load the game useing shortcut or progams/totalwar and what version do you have just MTW or MTWVI in the MTWViking Invasion you don't need to be patch up.I have DX9.0C and I have no problems.
Did you do a fresh intall of the game lately or when you unistalled it did you delete the game folder.I hope some of this helps as I am not as knowledged in this game as I am in my Trek games.What else have you done or haven't?