Someone else with this problem said you just have to quicksave before you talk to each of them, and load the game to try again if you have a problem.
Welcome to the forum.
However, since quicksave by its nature overwrites a savegame, and overwriting savegames tends to corrupt them on both 360 and PC, I wouldn't necessarily recommend that course of action.
I suppose you could delete your quicksave then hit the quicksave key.
