Vereth the Cunning keeps disappearing - can't complete quest

Hi,
I'm having an issue with the npc Vereth the Cunning located in southern Icecrown. I accepted a quest from him, but when I try to turn it in, he disappears every time I get close to him. I fly/run away and he re-appears. Then when I go closer he disappears again. Is this an issue with the general area he's in (I think it's Court of Bones or something?) If a fellow player is there, they also disappear. I noticed some enemies needed for the tournament dailies also disappear (the mounted daily quests)

Someone suggested that I just try to fly up and click as fast as I can and HOPEFULLY try to compete the quest, but there's no way.

Please help!