On the quest "Waking Nightmare", right before the objective to get the skull, Erendur freezes. Preventing me from continuing the quest.

Hi,

The quest is quite glitchy, have you checked here? http://www.uesp.net/wiki/Skyrim:Waking_Nightmare (Bugs section)

I am having the same problem. He is suppose to take me to the library but just stops halfway. I am running the latest beta, I don't know if this worked before.