[dnanian]

OK, from this I can see that the drive *has* failed before -- you can see that it's now mounted at "Big D 1" rather than "Big D".

To clean up the mount points, restart the machine. Then, give the backup another shot -- but, before you do, check the manufacturer to see if there's a firmware update available for the drive. You might also want to consider using Disk Utility to erase *AND ZERO* the data and free space, to ensure that all bad sectors are remapped.