the backup wad not performed because an error occurred while copying files to the backup disk.
The problem may be temporary.try again later to backup.if the problem persists,use disk utility to repair your backup disk.any body help me...!
Not one of Apple's better messages.
If you haven't found it yet, see #C3 in Time Machine - Troubleshooting. TM is likely having a problem with a file, and that will show you how to find and fix it.
Guys and gals....
I seem to have sorted this issue out! I disconnected from the internet (Airport Off) and then turned my Magic Mouse off and it worked fine. I don't think it was my mouse if I'm honest. I think it must have been things like Facebook Update Notifications! Must have interrupted certain files but it's worth a try. Worked for me so am all backed up!