I actually got it to refresh by turning off WiFi and relying on 3G.
I'm not sure if there are Gremlins with the WiFi, or if they're gone, but now I'll turn it back on and see if it still updates at this time tomorrow.
If not, I absolutely will try the "Check for New Content" option in the library.
Thanks for the suggestions.
Doggoned Gremlins. Remind me to find out how to eradicate them, so I can write an ebook about the process and make sure all Nook owners can obtain a copy.