I just got all three DLC a couple days ago. I started working on Hearthfire first and it went smoothly. Then I started Dawnguard and played it through, and it worked smoothly. However, I just started Dragonborn last night and so far, 2 separate locations have been inaccessible. The first place was Gyldenhul Barrow, which I didn't really mind or pay attention to. I figured it was just a bug, and if I played more and came back, it would be fine. As a result, I decided to continue the main story. I made it to Miraak's Temple, but as soon as I reach the door to the Sanctum, the same error as Gyldenhul happens. The game starts to load the location, shows my level at top right, has some smoke float around, etc., then suddenly stops and freezes my console entirely. I'm lucky I have a console remote as well as my controller, otherwise I'd have to unplug my console. What is this and why is it happening?

Have you tried to clear your XBOX 360 cache ???

http://support.xbox.com/en-US/xbox-360/system/clear-system-cache

Forgot about that lol. Did it and Sanctum immediately loaded

Cool...continue your journey, and have fun.