I have the 811 and another older receiver, 2700 I think. Both do it so it's not just the 811. On the 811, if you go out far enough, it will download but it ends up back to the current time with the same no info message beyond an hour or two. strange... Also ment TV guide, not TC. (The fingers don't work well today!)
My new 301 is starting to have a similar problem. It works fine as long as you shut it off every night. If you keep it turned on it needs a reset every two to three days. We never had to do this with our trusty old 3800 and my wife is starting to get annoyed.
My 301 has been doing it to. If you scroll forward several hours you will find guide data. Then when you scroll back the missing data starts to show. You never get a downloading guide message, and the whole process takes 2-3 seconds.
Mine has done this right after it has done a guide download. Has been doing this for a week or two.