Error -556 (backup client: network interface unavailable) generally means that the network interface you used to log in the client is no longer working. The solution is to correct your network interface configuration or else configure the client to connect via a different interface.
To edit your interfaces on Windows click Configure, then Clients, then click the Interfaces toolbar button. On the Macintosh go to Preferences to change your network settings.
Last Update: February 13, 2012