Posted above:
I saw a theory proposed in another thread which I believe may have some merit. If the last OTA channel that you tuned is marginal, it may be affecting your ability to lock on a satellite channel also. Often my wife will change from channel 7.1 (KABC Los Angeles) which is one of my weaker OTA stations and then cruise the VOOM channels. There can be a lot of audio dropouts or video blackouts. I think that if she left the OTA tuner on channel 4.1 which is a stronger station, maybe the satellite channels wouldn't experience the problems.
It could be coincidence, but it made my problems go away.