Norton Ghost version 15.0.1.36526

I keep getting the following Error Cannot successfully reconcile changes since last session; yet when I open Norton Ghost Panel it then shows it is backed up. Backup to external usb hard drive.

 

Full error as written in event viewer: 

Event Type: Error
Event Source: Norton Ghost
Event Category: High Priority
Event ID: 100
Date:  10/4/2011
Time:  2:47:48 PM
User:  N/A
Computer: HOMEDESKTOP
Description:
Error EC8F1780: Cannot successfully reconcile changes since last session.
 Error EC8F1771: Cannot enumerate the current drives on this system.
  Error E0BB0147: The operation 'Snap Volume' is not currently enabled for this Volume. (UMI:V-281-3215-6016)

Details:
Source: Norton Ghost