Incorrect function.(0x80070001) while performing a Vista Backup to a USB external harddrive

"To solve my problem,

A disk check on the drive I was backing up, found a broken sector that it was able to repair.

This appears to have prevented the shadow copy from functioning successfully.

After the disk check fixed everything, the backup proceeded successfully.

To perform a disk check

Goto ""My Computer""
Right click on the drive in Windows Explorer
Select Properties
Select the Tools tab
Click ""Check Now..."" under Error Checking
Make sure ""Automatically fix file system errors"" is selected
Select Start
You may need to restart your computer for the scan to occur if you are scanning your boot/primary partition."