We have our Quickbooks file on the server.
Quickbooks is installed on all computers, and use the Quickbooks file on the server.
The backup location for the Quickbooks file, is on a NAS drive which is joined the domain.
The backup folder (on the NAS drive) is mapped to each computer, and Quickbooks points to the map.
When performing a backup when Quickbooks is open (File/Backup company/Create local backup/Next/Save it now), its perform a successful backup.
BUT when Quickbooks lunch a backup upon exiting the program it give an error.