I had a problem like the one Deejus described: I was able to work around it by: Restore from a save immediately before speaking to DelphineGo outside and kill the vampires coincidentally attaching RiverwoodGo back in and speak to Delphine.Note that just exiting and re-entering the inn didn't help. Killing the vampires, or something else that happened while I was killing the vampires, made a difference. I noticed that she wasn't walking around as usual while I was experiencing the bug. She was always stuck on a single spot on the floor, a few feet in front of her husband's counter and the alchemy table. Even if I repeatedly attacked her, many guards would enter and attack, but she would never move from that spot. When I left the inn and immediately re-entered, she still seemed stuck, and still wouldn't follow me to the room. But after fighting the vamps outside, then coming back in, I noticed that she was walking around the inn again. Talking to her then worked. So, I think the root cause for not moving forward with the quest is that she can't move around, so she can't follow you. I don't know what's causing her to get stuck. If I had to work around it again, I would avoid asking her about the attic room until she's moving around freely. If she seems stuck, go kill things for a while and come back.