I got one of these (the 2 HDMI version) yesterday. it worked perfectly.
Shut my PC down and turn the screen off at the on/off button.
It hasn't turned on since! The power brick light is green/on...
EDIT: So 1.5hrs later I tried the on/off button and it just turned on as if nothing happened. It has been fine since. I unplugged it and it has worked fine since plugging it back in.
I haven't turned it off with the on/off button, though. That is a big "DO NOT PRESS" in big red letters now. Still no idea what the problem was...Edited by Timse - 1/26/13 at 1:24pm