I have only had my NOOK HD for a couple of months and it's been great. Today, when I turned the device to read the screen in LANDSCAPE mode, it didn't change - it just stayed in PORTRAITmode. I am not reading a book, which I have read can be locked in one mode or the other, but rather, just using FaceBook, email, etc.
I appreciate all responses.
Jules In CA
Make sure it didn't accidentally get locked in portrait mode. Tap the settings icon and make sure 'lock rotation' is off.