I just bought home a new Xbox 360, hooked up with my HDMI cable and the display worked perfectly. Then started the nightmare. I did a latest update with the console and display went blank and every time i started the 360 it gave “Display mode not supported” and there was no display. Even resetting the console (holding Y and RT) never worked for me no matter how many times i did resetting the console. I was using samsung 19” LCD TV with HDTV ready along with my Xbox.
I was very frustrated with this problem because initially the display worked at HDMI 1080p and now no display. My HDMI cable, Xbox were just everything fine after doing a thorough checkup. I had a weird feeling that update has got to do with the display problem.
I somehow fixed the problem by blindly playing with controller keys. Here is how you fix the problem to restore your display. Remember you have to do it blindly
Start Xbox and wait 1 min until it comes dashboard.
Press XBoX Guide button
Press RIGHT (2 times)
Press DOWN (2 times)
Press A (4 times)
Please note these settings are latest for new xbox dashboard. Now you will be in display settings in xbox (blindly)..
Now chose any one of the following…
Press UP 3 times then A -> Optimal settings
Press A -> 1080i setting
Press UP then A -> 720p resolution
If there is no display, again..
Press UP then A (see if display comes up)
I got back my display back with UP and A second time and keep repeating the above step until you get the display.
I have seen this display issue with many people who done updates and hooked up with HDMI cable for Xbox. I hope this helps.
