I'm on the quest Put The Best Down for the Dead Money DLC on Xbox 360. I get to the point where I Turn off the gas valves, Dog chokes himself, I loot the maintenance key and run like hell to the Casino Lobby. Once I make it to the lobby, I'm safe from blowing up but the quest doesn't mark the last task as completed. I've even went back into the kitchen - Dog is nothing more than a few pieces of meat on the floor and the gas is turned off, but alas I can't progress further in the game w/o finishing this task. Help?