1. Disconnect the AVR from the TV.
2. Delete that HDMI input in the Input Name menu.
3. Use the System Reset (small resessed button under the front control panel.
4. Reconnect the AVR to the TV HDMI input.
5. You should now be able to see the picture of from the AVR to be able to see the AVR menu. Enter the AVR menu and turn off the CEC or HDMI Control feature.
The Mitsubishi is compatible with HDMI CEC (Consumer Electronics Control) for DVD and Blu-ray but not for CEC for AVRs. The message you are getting is the AVR trying to establish an CEC connection and the TV responds that it is not compatible. If you turn off CEC in the AVR menu the problem should go away.