OK, I had a friend with both a Windows and Linux box do some testing for me. He had tcpdump running on the Linux box and was using the stock Windows Rio server. He attempted to store a favorite: it didn't work. It seems like this feature is totally broken (which is kind of hard to believe). He didn't see any UDP traffic via tcpdump either (which is consistent with the feature not working and also consistent with the behavior of my Rio).

Any ideas?? Does the Rio, during initial boot-up, do some kind of probe or handshake looking for a server on port 18678 and, if it doesn't find it, never send anything there again?