Are you talking about the quest after 'Full of Mystery'?
I'm having the same problem too, but I think it's due to a bug that's been going on lately where a quest will pop up for you to accept after another quest, but when you click to accept it, it doesn't really accept and you have to open the dialog all over again to 'really' accept the quest.
The problem with the quest after 'Full of Mystery' however, is that there is no way to do this, because there is no npc that gives you the quest. I found Folum's body, completed the quest, his body dissapeared and I got the 'fake' accept a quest screen appear.
So now I'm stuck. ><