Windows PCs under Shared Connections getting removed after adding (Servers are staying added).

When I add "Windows PCs" under 'Settings -> Shared Connections' they show as added initially, but eventually they disappear.  I keep re-adding them, but they keep disappearing, and nobody else can ever see them either.  Any servers I have added are staying put and are viewable by all other users.  Why would the Windows PCs disappear but not the servers?