BFCoughlin, Nothing I can think of.
The way it works is that Facebook requires an App or Website (Which is what I'm guessing the Nook Device is treated as) to use an Authentication protocol. And then it takes in your password and id via this protocol and logs you in.
It might be a problem in
1) Facebook's servers. For that trying again in a few hours would help.
2) 'Permissions' in whatever app/code Nook uses to connect to Facebook. Again, trying in a few hours would help as they would fix it pretty quickly for something big like facebook.
3) Problem in the Authentication Protocol. No idea what the fix would be here.
4) Something else entirely.
The last thing is that it might be something with your B&N account and that's preventing you from logging in to B&N. This seems unlikely but the message you are seeing seems to suggest this happened.
Can you log in to the Nook website?
Weirdest damned thing...I've tried over the course of the last two days and nothing happened. Could use the B&N FB app; could log into B&N. Just now, I picked up the HD+ to make sure I had documented this before I posted & decided just out of desperation to check the "add FB friends as Nook friends" box. And now I'm linked. I do not know if it's because I added that factor or if it just happened because something on their end got fixed. But I was able to share the quote and it's on my FB page. Mysteriouser and mysteriouser.