Confirmed the methodology of colin415, with slightly fewer steps. Retrospect Single Server 7.7.325, hotfix/update 22.214.171.124. Clients are Windows XP Pro (32-bit) SP3, Retrospect Client 7.7.106. - Removed Retrospect Client entry from Windows Firewall exception list. - Uninstalled Retrospect Client. Reboot. - Deleted the Retrospect folder in Program Files, including all contents. - Searched the registry for "Retrospect" entries and deleted the ones that made sense. (There is one that is a subfolder of "Dantz" so I deleted both, and I ignored any that did not directly refer to the Retrospect Client.) Reboot. - Installed the Retrospect Client normally again. Reboot again if so inclined. - Deleted/Forgot the Backup Client entry on the server. Added the Backup Client normally again. So far so good. Some of the clients did not respond well to an in-place update of the client from 7.6 to 7.7 (we upgraded our server license from 7.6 to 7.7 via an entirely new physical server - avoided server upgrade problems). Error -560 was the most annoying. After wrestling with a few clients using colin415's method, which fixed them completely, we decided to take the time to do this to every single Windows-based client. It has cleared up quite a few quirks of the others, as well. Backups are all happy again!