The attachments seems to show the drive to which you are backing up is not connected. You did cover some of the info on in the windows that might have been relevant.
Are you doing a System Image and File backup? Have you looked at what is being backed up to make sure it is not trying to backup a previous backup, or other data. If you are doing both, you might try just the system image to see if it will complete. And just to make sure, the second drive, is a physically different drive?
Joe mentions going to a third party utility, and that might help your situation, but I use just the Windows Backup and Restore for my Images and don't seem to have any problems. But let us know, and possibly explain when the "Disconnected" annotation shows up during the process...