The quest chain is fine through part 3. You receive thePulsing Fragment and go see Dennison. Part 3 completes. You click on the highlightedtext for part 4. There is no further quest text. Dennison does not give you thepulsing fragment back. When I open up my quest log the gold box shows up withthe quest title, but there is no black text box attached to it.
I went to the Clerics tower and talked to the archbishop tosee if the quest would advance. No such luck.

On a side note what level is part 3 supposed to be? I earned a couple of death points completing it as a Lvl 69 warrior.