Playing Druid (2

/ Mage (29) in Coast of Opportunity - Basilisk Pit
The Quest [29] Dangerous Mission seems to be bugged. I get the quest - go to the pit. There is an NPC at the entrance. Fight my way to the room with the second NPC who says "kill the snakes" - I killed them all, slowly. After the snakes, she wants you to target the crack in the runestone and attack it.
I have tried tab, clicking on it, standing in a half a dozen places. I've tried ignoring the snakes and trying to target the stone as was suggested on a german thread.
The trouble is - the stone isn't a valid target - you can not attack the stone. There is no crack to hit - so the quest fails - repeatedly.