Dual tuner setup changing channels on its own - help

[tvmaster2]

I have both a HD-PVR and a PVR 150 installed. I have split the channel map between the two tuners so that the HD-PVR only sees the HD channels (h.264) from my satellite receiver in its map, and the PVR-150 only sees SD channels (mpg2) in its map.

For a few weeks, everything worked fine. However, out of nowhere, SageTV wants to consistently change channels to channel 605 (a standard def channel mapped to the PVR-150).

SageTV even allows the channel change when I am recording from the HD-PVR. I can't seem to make it stop. I checked favorites, and found no evidence of channel 605 there. The change happens when a program is scheduled to begin on channel 605.

Any ideas why this would be happening?

The only thing I can think of as a solution - if I had a HD200 media extender that wasn't on standby and sitting on channel 605 - if that was open and active, would it keep changing the channel on the server?