This has happened many times - most recently about an hour ago (2 pm PST).

I select new posts - get a list (this time some small number of 100's AIR), start going through, read a few, at some point when hit back button to go back to thread get message like "search cannot be completed". go back and start over - now I have about 50 "found" in my search

Most of the time it works well, can't figure out why sometimes it resets at random tmes and then gives me may fewer "finds".