Comment 6 for bug 1315369

This is really strange... Because it's weird that the keyboard works once to go to tty1 and then it stops to send events...

Anyway I would say at this point that unity doesn't seem to be the guilty here.
Just another way, to make sure this is the case, enable the OSK (this would fallback to the old gnome-screensaver):
  gsettings set org.gnome.desktop.a11y.applications screen-keyboard-enabled true

Then give it another try, if you still get this problem, this is definitely not an unity issue.

Use this command to reset the on-screen-keyboard setting afterwards
  gsettings reset org.gnome.desktop.a11y.applications screen-keyboard-enabled