[ubuntu] ubuntu shutdown-screen flashes & shows ^[[2~ characters.

I am facing some strange problem in ubuntu a few times. I'm using 14.04.04 lts.

after shutdown, the screen shows ^[[2~ ... & dont shutdown at all & flashes untill the battery is fully drained.
I dont know what it means by those characters & a similar issue I faced yesterday on "update information" window after clicking 'run this action now' button. the Terminal window was filled in by ^[[2~ characters.

Does anyone know what could be causing the problem, and how to fix it?