It happened again last night .... Turned on H21 to find blank screen (no audio/video) "stuck" on Channel 0-0 with "Searching for satellite" message on screen. Could not change channels or view Guide data. Checked satellite signal levels and all looked good. Got a brief flash of audio/video after checking signal levels, or performing a System Test, before it returned to Channel 0-0 again with no audio/video. Sometimes the System Test would show "Tuner Failed", but not always. Menu Reset fixed it again.