I had the same problem also. Finally I went out to the hall, dropped all my special items (everything, even if not related to this quest), and picked them up again but if you have more than 1 rune, make sure you pick up only the WISDOM rune.
I don't know if it was the dropping/picking up items or having only the Wisdom rune that fixed the problem but it finally got the guy to start the summoning.
