Gents: With your help, I was able to narrow the problem to the destacker. After a couple e-mail exchanges with Mark McCorkle at 9th tee, he had me check the DC voltage of the incoming signal. He concluded it was very low, and may not be passing signal appropriately. He also stated that in his experience, he has never had a problem with a Sonora dual destacker. Sure enough, I called a service technician out, and while he had no idea what was wrong, I suggested we put a line amp in, and voila, both transponder sides and the Tivo works as you would expect. Of course the technician did not realize that he could not put the line amp before the destacker because he effectively cut off my terrestrial antennae, but I am off to home depot to pick up a second line amp and to rectify the situation. My sincere thanks.