I have thoroughly enjoyed this game until I hit this brick wall.
  
  I stood in the treasury room and acquired the winter ring.  I also have the winter amulet.
Now the quest won't close at all.  And yes I've also opened up his tomb with the special book from the librarian.
Oh and I see someone has the exact same issue:
http://www.larian.com/forums/ubbthreads.php?ubb=showflat&Number=509590Why hasn't Larian fixed this bug?