I know there was discussion earlier in this thread about Fable III having this kind of problem, but I never thought I'd encounter a game-breaking bug, which I think I may have here...
I think the game assumed I was further ahead on my quest progress and lead me to a point where I can't do anything. I regrettably saved my game at this point, (like I said, I'd never encountered a game-breaking bug before in my life), and I can't seem to get around it. I've reloaded my game save, turned the Xbox off and on again, and disconnected my internet connection. Unless anyone suggests any other alternatives, I suppose I'll have to start over.
Sucks to be me, I guess.