Does it say - Home is not responding.
Force Close & Wait?
If so, it's a standard Android dialog that's displayed when some app stops responding. App = anything, even the home app or the app installer app.
It just means that the Home App - basically the 'Home of the Device' - the Nook skin/OS skin is running into problems and not responding. You can press Wait and see if it starts responding in afew seconds.
It might mean you have too many apps working in the background and they aren't leaving enough memory for Home to work properly.
Just get app killer app from Nook Store or any app manager app from Google Play store and find out which apps are being naughty and then disable them.