The Diamond key door is what I am stuck on, I have the correct combination and they key will go in and turn, but the door remains closed. I have already tried reloading saves/restarting the consol (Xbox 360) and going out of the tempal and back in but none of it seems to work. Did anyone else run into this problem but got passed it? If so how? Please help.

If this is DG related, you are in the wrong forum matey. Thats what the very first forum, the one that says Dawnguard, is for.

If not, disregard.

I am not in Downguard this is on the main story line, the quest is "The World Eaters-Eyrie"

Aight, sorry mate, tried looking on UESP?

What is that? lol

It's a wikia.
http://www.uesp.net/

http://www.uesp.net/

Its like a reliable elder scrolls wiki. If its a bug, fixable or not, it should be noted on there. If you are missing something it'll be on there too, just go to Skyrim, then to quests and choose the quest you need and check the walkthrough and bugs.

Heres the page you want: http://www.uesp.net/wiki/Skyrim:The_World-Eater%27s_Eyrie

EDIT: Ninja'd >.<

Alright, thanks guys

This happened to me not too long ago. Door simply would not open.

I logged off, turned off the computer, went to bed. Next day, it was working fine.