one of my client machines periodically loses network connection with the server (have run all troubleshooting/diagnostics on usual stuff..NIC/cabling etc) .. first of all there was no connection at all, couldn't ping etc, then managed to connect partly to the server and the rest of the network and finally when trying to map network drives on the client, an error message came up saying "No logon servers available to service logon request".. can anyone explain what this means please?