The upgrade came last night while I had my NC on the charger. When I took & unlocked it it was stuck in "shop" mode on one of the app descriptions. (was on home when I put it on the charger last night)It was just flashing & rapidly cycling through the description pages of a number of different apps. I pressed"home" but all that happened was that it was stuck on an app description for something called "Pepper Pot". This would not close & just kept flashing & cycling as if pages were being turned. The only way I could get it to stop as to turn off the NOOK. I had to hold down the "off" button for nearly a minute.
When I turned it back on I saw the green N & realized the upgrade had been downloaded. All seemed well. Later this afternoon I went to read a library book & had been reading. It said "Error-User Not Activated." Same thing with 2 other books I had sucessfully downloaded yesterday. I figure the somehow the upgrade had overwritten my ADE authorization. Pluged in the Nook & reauthorized the device. Detached Nook & tried to open books again. When I tapped on the book it said "Item not found." Plugged books back it. According to ADE books were on Nook but figured I would try sideloading them again. Asked me if I wanted to replace files, said "yes". Detached Nook again. This time error message said "Item not downloaded." Nothing left to do but try turning Nook off & back on. This seems to have worked. Have not tried yet to access any other sideloaded files.
If you have this kind of weirdness try turning the Nook & on before any of the other troubleshooting steps I went through. However, the first shut down was to stop the "flashing" problem. It may have stopped the problem & allowed the upgrade to take & changes to be made to the system. However, it also may have allowed the ADE authorization to be overwritten. A re-authorization of ADE & a second reboot was required to allow that change to take place. If you haven't shut down your Nook since the upgrade you may not notice the "broken" ADE link until you do. It wasn't hard to fix, just a pain.