I'm getting this error message when backing up to both my Time Capsule at home and my Western Digital at the office.
The backup was not performed because an error occurred while copying files to the backup disk.
I've tried repairing permissions on my MacBook Pro and the backup sparse bundle itself and the external volume. Nothing seems to work. It seems like there's some corrupt file in the sparse bundle backup that is not allowing it to back up. Other computers on the network are backing up okay to the Time Capsule.