I seem to have a problem with Windows Backup when a scheduled image backup to an external hard drive fails to complete, although it has worked successfully before on many occasions. Windows Backup reports an error code of 0x8078012D.
I have run the Error Checking tool on the external drive with both the repair options switched on, but no problems discovered. The external disk drive seems ok as I use a Norton program to back up data to the same drive without any problems. Also Windows Backup will happily do a 'non system image' backup on the external drive.
But it will not do a stand alone system image nor one as an add on the a normal backup.