I can now reproduce this any time a hard reboot is done and the 921 comes up in 480 after rebooting. I bring up the Display Setup screen (menu-6-9) to change to 720 or 1080. I move the cursor to another display resolution. As soon as I press Select, the resolution changes and user input is locked out. There is no way to leave the screen directly (either by cursoring over to the on-screen Done button, or by pressing cancel on the remote). The only way I've found to leave is by pressing Guide (or sometimes DVR). After leaving one of those screens things are usually ok. Even this has sometimes failed, with the background image (the green shaded screen with the Dish logo & logo shadow upper left) refusing to go away. A power off & back on again seems to clear up the stuck background image when this happens.