I needed to move a vRanger Repository, but didn't want to start all my backups over, so I found a handy article from Quest that identifies how to do it.
FYI, I believe it requires vRanger 5.3 and up.
The basics are you go into SQL Management Studio, expand down to dbo.Repository to identify the repository, and change the host or target directory. Then go to dbo.RepositoryCIFS to change the sharename.
Make sure you restart the vRanger Services after making the changes.