1080P

I have the same problem. When I go to settings to change the res. 480 is permanently selected. I can check 1080P but when I move to the next screen everything goes dark. My PS3 is connected to a Sony KDL46XBR6. I use HDMI cables. 1080P res was working fine 1 week ago, I turned it on the screen was black and I had to reset the res. Now its seemingly stuck at 480! Argh!