Backing up with Windows 7

For the past month or so I have been having troubles backing up my computer using Windows 7's built in backup and restore utility as some of you already know. After cleaning up my 1TB drive I have gotten the backup to go as far as 97% without a problem, Once it hits the 97% complete I get the following message:

Backup encountered a problem while backing up file C:WindowsSystem32configsystemprofileDocuments. Error:(The system cannot find the file specified. (0x80070002))

Does anyone know how to fix this issue? I would really like to backup my files with my external drive.