It's a royal pain, but try that direction antenna 45 degrees off of straight at the towers. Then try 90 degrees. Then keep going in increments of 45 degrees until you've come full circle. That's mostly to eliminate the unlikely. Then redo Guided Setup and give it a different zip code for an area where the problem channel is still available OTA, although the farther away the better perhaps, or maybe better yet, a zip code for an area of the country where an entirely different station is available on that same frequency. If the good channel and the bad channel are only separated in frequency by the same amount that the old analog channels 8 and 9 were (6 MHz), there's almost no way it's a hardware problem, especially one that's also present in the replacement box. So I'm thinking "software that runs the hardware" problem, and since this isn't happening to TiVo owners all over the country, I suspect the problem is in the software specific to your location.