Anyone else having problems sharing libraries in iTunes?

For the last few weeks (or, ever since I upgraded iTunes), my computers are not seeing each other as shared libraries. All three of my computers (2 pcs, 1 mac) are having this problem. Occasionally the two pcs can see each other, but that's it.

Additionally, the iOS "Remote" app isn't able to connect to any of them either.

Anyone else having this problem? Very frustrating.