When you are trying to play a part of skyrim that you have to get by following a quest line, but not doing the quest, it "breaks" the game. There is a way to finish a quest line by using the tilde key and entering the right sequence of commands, but you need to read up on it.
Its probably more fun to play the story line instead?
Stay out of the Forts! if you have not played the choosing sides and War part yet? That"s a game breaker!