smartware - backed up files count is decreasing

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http://superuser.com – A friend has the WD Smartware software installed. When she clicks on 'backup', the number of files backed up is decreasing, even though the files to back up count is much larger than the count of files that are backed up. She paused the backup and quit. This behavior seems somewhat disconcerting (and they haven't noticed it before when backing up) Is this normal behavior? I could see that if files had been deleted from the main drive, and it was deleting them from the backup, this might happen, but would expect the software to keep a backup of deleted files also, unless the drive is full (an (HowTos)