My $.02 worth....
I have had this very same experience, at the exact time in this quest.
The first time I walked away for a couple minutes ( I tend to do that when the console freezes no matter how much I want to walk over and kick it through the wall). I came back and it appeared to be locked up, so I restarted console via its on/off button, it happened again. Frustration level increased... :(
I held down guide button, heard the noise rma mentions, but it still did not shut off with controller input.... I have the long white remote that runs the DVD options for the Xbox 360 Elite... it's on/off button turned off console. Restart.
Having read about other Skyrim glitches in this forum, I decided to erase the cache and save files except for about 5 or 6. Viola! It still took about 45-50 seconds, but the quest continued as it should. The wait is built into the story line to heighten the suspense, IMHO. Certainly not for five minutes tho.
Quick to judge, quick to anger, slow to understand. Ignorance and prejudice, and fear walk hand in hand.