Make sure the screen is clean. If that's not an issue, contact CS again. You might want to see if they'll replace it, since you say it's less than a year old.
I see you had the same problem I have,in that the screen of your Nook HD+ goes MENTAL? I relate it to watching a DVD Movie in FF search mode,how does that sound to you?. Anyway...may I ask how you got on in the end.
For my part,I've had a VERY strange turn of events,after a "chat" with Nook's CS On-Line chat..Picture the scene (short version) I purchase a Refurb from an On-Line business seller (ebay) On the first day of use it goes MENTAL,I surf the net,end up with a chat to Nook,and they say I should return it to THEM (Nook) for replacement.
So jenny...how did you get on with yours?
All the best