you can try a reset, go in to settings (if you're at all able) then device information - erase and deregister.
I don't think that's gonna fix the issue honestly, but it's worth a shot.
You can also call BN support, or visit a store. Given the recent history we've seen here on the forum I would suggest the store.
It's also worth giving your screen a clean. The NST uses infrared sensors that need the small gap between the screen and bezel clear. You might try blowing that out. I have one unit that goes nuts regularly until I give it a good blast to clear out any dust.
I am having the same problem with my Glow. Worked fine until I had it in a case with a couple of CR2032 batteries in the cover next to the screen, although I don't know for sure if that's related.
Cleaned the dickens out of the screen and bezel but that didn't help.
Stuck it in the fridge to punish it ; actually to see if the dry cold would reset it somehow. It works when it's cold but as soon as it warms up it goes wrong again. On the search screen, touches at the screen top activate the bottom row of keys. Oddly enough, the choices brought up by the "n" (home, library, etc.) work OK. But "power off" requires another stint in the fridge.
'Way out of warranty, of course.