Our normal nightly ritual is that Channels gets activated (it was left in Guide view, having exited from live TV in the morning). We switch to Recordings and occasionally the new recordings from this evening do NOT show up.
I tried switching to other Navigational items (e.g. TV Shows) and the new recordings did not appear. I only realized the recordings had to exist because the guide showed the second news broadcast we record each night in yellow (e.g. recording in progress). That's when I decided to force quit channels and restart it, which caused it to talk to the server and refresh.
In case its relevant, I believe the last two times we did this where I noticed the problem, it was between 6 and 6:30p, the first news show had been recorded and the second show, immediately afterward, was in progress.