Numerous people, notably David Hertzberg, have questioned whether using Storage Groups is a good idea. We have been using a Disk Storage Group media set for over a year with no particular issues until last week, when we started getting strange errors for two clients:
Can't access Backup Set [Username], error -2262 (Catalog File in use by another machine)
Neither quitting and relaunching Retrospect Engine nor rebooting the backup computer made any difference, and when I attempted to rebuild the catalog, I was unable to do so because Retrospect failed to accept the media set's password. (And that even though the media set was configured to remember the password for any access.)
This issue cropped up shortly after upgrading to v18.0.0, which may or may not be relevant.