yeah same thing happened to me with the old comcast cable box and then the new one worked great. until I bought the PS3 that works on and off... - well at least it works and I can fix it by switching the input on my AV receiver.
the bad news came when I bought the xbox 360 elite, that thing never showed a normal picture on HDMI
also, I recently got the popcorn hour 110, same green screen over HDMI
so wait a minute, the only hdmi devices that work every single time are...