A GPO is backed up to a DVD. The GPO has existing settings. When importing from this DVD some GPO settings cannot be edited. This does not occur when using a file share location for the back up.
The problem is that the files get marked as 'read only' when they are burned to a disk, and when Windows imports those files back to the SYSVOL it keeps the permissions and the manifest.xml is still marked as 'read only'.
Use a file share to backup GPOs.
Alternately, in the case of using a DVD, ensure that the "read only" permission is changed when the GPO is imported.