all of people have this problem with the 360 its a handshake problem between tv and 360 the 360 is pikky about tv brands models etc etc
https://forums.xbox.com/en-US/thread/4457E1C8-639C-485E-AD81-76F48FE71AF7?page=1
I have had this xbox hooked up to this TV for a while, it worked fine but i have not used it in a few months and I think it forgot the video settings, now its defaulting to 1080p put the TV can only do 1080i, I have tried the following solution
"1. Connect your 360 to your TV with the included composite (Yellow, Red, White) cable .
2. Ensure you're running the new Xbox dashboard (Avatars support).
3. Ensure no profile auto-sign's in at boot up.
4. Power off 360 and TV. Connect the HDMI cable between them.
5. Hold down the controller's xBox button for 3 seconds to power on, and wait for about 20 seconds.
6. Press right on the (dpad) left analog stick 9 times, to navigate to the System Settings menu.
7. Press the A button 4 times. (This will go to System Settings, Console Settings, Display, HDTV settings.)
8. Press up twice on the (dpad) left analog stick. Press A.
9. If no picture appears, wait 15 seconds, Press up again and press A. What you are doing is selecting lower display resolutions. Once you have a picture, you can try other higher resolutions, if you want, and it will revert back if you don't confirm it is ok. The 360 will remember the setting you finalize."
that does not work, I know its not signing me in because its not connected to the internet but still it does not work, I also do not have a component cable (well I do, but it doesn't seem to be working either) how can I fix this?
I also tried holding Y and R2 while it booted up but that did nothing.
more details:
I have tried 3 different HDMI cables, my PS3 works fine via HDMI on the same TV, I've tried the cable I use for the PS3.
and I know it is on because if I hold down the xbox button on the controller and press up twice then X the 360 shuts down.
There are known issues with HDMI Handshaking needed for HDCP. HDMI Handshaking occurs when each device is plugged in / turned on. Unplugging a device that uses HDMI destroys any existing handshaking that occurred previously. The steps I listed are to resolve HDMI Handshaking issues.
For more information:
http://www.google.com/search?q=hdmi+handshake+problems