It appears the Replay is busted. The DSS receiver is putting out a signal, the cable to the replay is carrying the signal, but whatever port I plug into, the replay doesn't see a signal. Not even from the antenna port, which - tho it doesn't have an antenna connected - should at least show a crappy signal on 5. So, we're now a single-DVR household. Murder-Suicide will ensue shortly.
It may be time to move up the time table on the Myth box.