I broke down and called DirecTV on this a few days ago. They said their technical team is aware of this and is working on a solution. It is apparently a software issue, as you are suspecting. The fix is supposed to happen via software update, thus from our point of view, the problem is supposed to simply go away on its own.
We now believe on our TV that it freezes up when we scroll to the last item on the "List". Both my husband and I have had that happen, and now we're afraid to scroll all the way to the bottom, LOL We are probably completely wrong about that, but you know what these kinds of bugs do to people.
I hope they're right and it corrects itself soon.