Just for giggles I put a blu-ray disc into my PS3 to see if playing a disc would properly fill the screen. It did.

It reminded me of another quirk in my system though. The PS3 welcome screen/menu screen has always displayed 4:3 as well. The PS3 is setup for a 16:9 tv, but it's always displayed 4:3 - except this time! When I turned on the PS3 it was displaying full screen (as it should!). I watched a couple minutes of the blu-ray, which also displayed properly and when I stopped the blu-ray playback, the PS3 screen came back up...4:3 again!

I'm really starting to think my Onkyo is whacked.