Not sure, but your comment makes sense. The Sony was using CBS previous to my reset. Now it's latched on to PBS. When I run the G*Factory Test, I don't see any errors and PBS seems to receive many more VBI packets more rapidly than CBS. Of course, this is not during any of the specified download periods.
FWIW, with the LG DVR it seemed (subjectively) that less guide channels meant less guide errors.
I chose the cable area yesterday morning, so the Sony had both the morning and afternoon download periods to get all the data. Maybe it has something to do with the first day of downloads after a reset. Everything is such a big secret with TV Guide that we don't know what might be happening, although there is a lot more knowledge out there now thanks to these forums.
The guide worked smoothly for several months until last week's problem. I expect that it will go back to that good behavior.