If you drop a quest and pick it back up, you do not lose items you gathered for the quest. Some of these quests are prone to breaking on Nostalrius, and this fixes them. Another example is the mass beast slaughter quests in Blasted Lands. If the NPCs refuse to take the turn in, you can just drop the quest, pick it back up, then turn it in.
This quest worked well for me ; I think that there is a general bug where some quests are not turnable when you have all the quest objects (I had the same problem with the 5 quests of the blood elves in the blasted lands, and some people had the same problem with Cyclonian). I hope this will be fixed soon.