Only other thing i can think of is that the hdmi channel is not setup for your ps3. I know with my hdtv i have an option of setting up a channel for gaming, blu-ray, pc etc etc. Unlikely to be an issue but you never know. I could never play my pc properly in 1080p through the tv because it wasnt selected as pc format. Once i changed it that fixed it.
So were you always playing your consoles in standard def before you got the new tv?