This problem just happened with the mission "Message to Whiterun". I'm on the part where I have to return the axe to Ulfric, but whenever I go there, I can't talk to him. I can however talk to guards and other people. I decided to try the Moonpath to Elsweyr quest line to do some unbroken quests. But when I got to Elsweyr, I can't talk to Yura, the person I need to talk to to continue the quest. It seems like I can't talk to any character that's needed to continue a quest. I had this before where I had to talk to the person in Markarth to do the first Dark Brotherhood assassination, and I couldn't talk to her, so I reloaded a save and continued without rejoining the Dark Brotherhood, and it worked fine. Now whenever I reload a save the same thing happens. Here are some pictures: http://imgur.com/a/2u61X