Home Theatre problem - help! "Unsupported signal. Check your device output."

[Pink Bits]

I have a problem with my home theatre set up. First of all, here's the gear I'm using...

Sony KDL-46Z4500 - 46" LCD TV
Sony BDP-S550 - Blu-ray Player
Onkyo TX-SR876 - A/V Receiver

Today, I went to play a Blu-ray disc ("The Big 4" concert - 1080i), but no video would show up on screen and just a message saying...
"Unsupported signal. Check your device output."

While the video wasn't displayed, I could hear the audio fine. I then tried another blu-ray disc and it worked fine ("Pirates of the Caribbean" - 1080p).

I played a different 1080i disc and then a different 1080p disc, and sure enough, for some reason the 1080p/24fps discs work fine, but the 1080i/60fps discs do not show video on the screen.

I have also had a problem with regular DVD's in the last few months too, where the audio is fine, but big blocky colours will appear on the screen (mainly greenish/pinkish colours).

I was thinking that it was the Blu-ray player at fault (and still could be for all I know) but I turned it off and tried my (crappy) LG DVD/HDD player just to see if the display was working on that one and it wasn't either.

This leads me to believe that the problem is in the A/V Receiver or the TV, but I'm not sure by any means.

I have not changed any firmware, any cables, settings, etc. Last week I watched the disc with no worries and a week later, it won't display video. It might even be something as easy as changing a setting to something, but I don't know what it would be.

Any help for this problem would be great. Thanks.