Apple - How to approve "Unapproved caller" whilst installing the software?

It seems it's some kind of temporary glitch, as it usually helps to restart the machine.

Other suggestions:

• Reboot into Safe Mode, then Verify and repair drive

  1. Reboot and hold the CMD+R keys
  2. Select Disk Utility
  3. Click on the image under my drive
  4. Verify and repair drive

• You may try to remove the cache files/folders located in /var/folders directory (not recommended) or move them into Trash.

  Normally cache files should be cleared every few days by Launch Daemon (/System/Library/LaunchDaemons/com.apple.bsd.dirhelper.plist).

  If the files can't be removed, reboot into Single Mode, run fsck, mount the root partition and run rm -vR -- /var/folders/*. Which is:

  1. Start on single user mode: Hit the CMD+S keys at start-up
  2. At the line, type (after root): fsck -fy and hit the Enter key.
  3. Mount the root drive by: mount -uw /
  4. Remove the cache files by: rm -Rf /var/folders/* (make sure you won't do any typo!).
  5. Reboot by typing: reboot.