I have to say, the Jelly Bean update is the worst thing they happened to my Galaxy Nexus. It is slower, the unlock screen out right locks up, the Bluetooth fails randomly; I need to reboot the phone every day to keep it usable. Lets hope that it isn't the same for other hardware...
I think it's a bug. I found my unlock screen stops responding when I accidentally touch the Google Now button at the bottom of the screen (a circle made of dots). Touch it again and it will go back to responsive. I think Google Now hijacks the touch input somehow.
