Just for clarity, I used the updates and had the hidden settings app flashed on the sd card, but for some reason that app had no affect on versioin 1.4.1 after rooting. I turned on the option to all sideloading and still when I went to try to sideload it would be refused. The dialog to change settings would appear, I would click it, go back to the app to install, and again the dialog to change settings would appear, never allowing the install. All of this even after the hidden settings app was supposed to take care of this. So to me there is no question that in version 1.4.1 sideloading is still blocked. Of course, once I reverted to version 1.4.0 and then rooted, sideloading worked after clicking the option when the dialog appeared.
---------- Post added at 01:44 PM ---------- Previous post was at 01:39 PM ----------
One thing I noticed in the three Nooks I have rooted is that once root is completed that when you click the search from the Nook home search menu, you find that it has been replaced by Google Search and you no longer can search for apps, etc. in he Nook. You can get to apps by using the launcher, but you no longer have any NT search functions.
In regards to the search function, just click the "g" in the upper right hand corner and change it to "Apps". You should see a little down arrow under the "g" indicating that there are more options.
For the unknown sources fix, try clearing data for the superuser app then try the unknown sources fix again. I noticed on my nook, that sometimes after adding the superuser app, some apps are denied (not allowed) one of which is NTHiddenSettings (NTHS). If NTHS is not allowed superuser then it can't write to the database that it needs to.
If you are using my update.zip, it automatically applies the the unknown sources fix. I am using 1.4.1 and I can sideload apps.
I am assuming that everyone knows that NTHiddenSettings>Applications settings>Development>USB debugging needs to be check and Auto Mount needs to be unchecked to sideload. Maybe this is the missing step?