I don't know if this is a glitch or something I'm doing wrong, but here's the gist of my problem:

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?

Under some as of yet unknown reasons, the emergency door to Cantina Madrid that is supposed to lead you to the kitchen, takes you back to the room where the emergency door key was in, giving no way to enter the kitchen and completing the quest. This can be solved by starting and completing some other quest about dealing with the team members instead, then returning to the casino to enter the kitchen of Cantina Madrid.

http://fallout.wikia.com/wiki/Put_the_Beast_Down

I hope that helps and I think I understand your problem

Nevermind, I read your OP wrong

Did you turn off ALL the valves?

There are three valves to turn off, however I found it much better to take turbo, find Dog, and talk him into combining with his other self. Adds much more to the story. If your speech is not high enough though... :sadvaultboy: ...then you are back to being a plumber fixing valves and running like hell.

If these ideas don't work, then I suggest solving it the way I did. Play the Dog Command Tape and God should talk to you. After going through the dialogue (I think you may need 90 Speech), solve the leaks normally. Do not exit the room until your vision turns to normal, which occurs when you have successfully repaired the leaks. Hope this helps.

So I was able to complete the quest, but I think this is a bug none the less.

What I was originally attempting:
- Shut off Valves
- Get dog to kill himself (speech wasn't high enough to save him)
- Run like Hell to the restaurant entrance.

I would successfully get out of the restaurant and back to the casino lobby but it wouldn't complete. My collar would stop beeping, Dog's would explode, and I would be left stuck, unable to complete the quest.

What I did to complete the quest:
-Shut off Valves
-Get dog to kill himself
-Exit the kitchen by going back through the door I used to enter the kitchen

This method completed the quest. Defiantly a bug IMO, even if the restaurant entrance isn't an acceptable method to exit to complete the objective, the quest should still fail and reload me? Anyways, I'm through it, thanks for the suggestions none the less guys.