Priest in Peril help!?!? (Runescape)?

In the Priest in Peril quest, on the part where you need the key, I did everything (seemingly) right. I killed the lvl 30 monks, got a gold key, and swapped the key for an Iron Key. However, that Iron Key doesn't work. I've tried opening the door, and I've tried using the key on the door. Nothing. Help?