Has anyone found a solution to this issue? I just purchased Retrospect Professional and I am unable to connect to the one other client on the network. Using the "Test" feature I am able to verify that the host does have the client installed and running. In my Linksys router configuration multi-cast pass through is enabled. I am running Norton Internet Security, which I tried turning off on both the backup and client computers but that did not work either. Is there something else to try?