I just got a brand new Xbox 360 Elite like 2 weeks ago. Have only used it maybe 10 times since then, I play maybe 1-2 times per week, sometimes more. I had it hooked up with the HDMI cable to my 50 inch plasma. Looked and worked great. I took it to a friends house, had to use the standard A/V cable because the TV wasn't high-def. When I brought it back home, the HDMI out no longer displays and picture and I don't get any sound. Has anyone ever heard of this? The only thing I can think is that plugging it in with hte AV cable messed up the HDMI resolution. I read a post somewhere that said hooking it up to a 1080p tv might allow me to change the setting back to optimal. I have a 1080i tv not 1080p. I am going to try this later today, but in the mean time does anyone know what may have caused this and how to fix it? I already called MS and they said to send it in for repair or replacement. I really don't want to send it in because it is a jasper and i don't want them to send me back something older. I also already tried the Hold Y and Left trigger while it is booting. I tried a different HDMI cable and a different port on the TV.

Thanks,

-Jon

Return the 360 to its default settings (480i/p resolution):

http://support.microsoft.com/kb/911059

Yeah, I tried that on the phone with Microsoft, twice. No dice, still shows a black flickering screen. What is weird is that my TV even though it is 1080i, will display a picture at 1080p, it just downscales the signal. I have done it before with my 360.

Thank you this thread helped me to solve my no HDMI problem!