Hi!
The problem is probably that one of your files is corrupt. If you check which file gives you the error, you can just delete it & try again.
If you have problems deleting the file, you can work around it by going to the "advanced" section of the back up & selecting everything exept that file and then continue to back up.
Another know problem is the browser cache. If the solution above does not work, you can try deleting all you cache & try again.
