I encountered the following problem tonight. Played a couple of arcade demos for less than 1 hour then spent some time tooling around with NXE and finally was about to install Madden onto my hard drive after deleting numerous items as a test. Unfortunately I didnt hit Y when I went to do so and the game started to load. Since this was not what I wanted I pulled up the guide and hit Y to take me back to the dash. That's when it started. I could not get back to the dash after 2 tries and it appeared the system had frozen. I manually powered down and attempted to restart only to get the 360 to fire up and my Samsung TV display the message "Not Supported Mode." Tried several times unsuccessfully to get it work. After about an hour and no disk in the drive, it booted up for a moment and as soon as I opened the drive to insert the disk, my Not Supported Mode message reappeared. In the couple of hours since, same message regardless of what I've done: disk/no disk in the drive, switching the TV/HDTV switch, unplugging the Xbox component or power cables, unplugging the cables from the TV. I have also noticed that it takes almost a minute for the Xbox to fully power down after this episode tonight. Something is still running after the power button goes out and the power button even flashes once (like when its off but downloading) before finally powering off. I will admit that I have been using it in a mostly sealed entertainment stand but it had not given me any problems before tonight even when I logged several consecutive hours a couple weeks ago. Any ideas would be greatly appreciated. I was hoping my Feb 06 purchase would hold out until the smaller (slim) heating units become available.