Nightfall is BROKEN this week! (01/12)

According to an article posted on Kotaku:

…if for some reason you do decide to take on this week’s Nightfall challenge, you won’t make it very far. Around halfway through the strike—The Sunless Cell, if you’re curious—after clearing out a few waves of Hive and Taken, you’ll find that one of the doors simply won’t open. You can’t make any more progress. You won’t get anything. All you can do is leave.

Hopefully this link works: According to Bungie, the Nightfall has been fixed.