I have a Seagate FreeAgent external drive to help with backups.

About 2 weeks ago, the nightly backup started failing. It was always one particular file that couldn't get copied and the error code was 2013.

A number of sites from the Google indicated that it was a file permission issue on both the backup drive and the source drive. I made sure that the file was not marked as read-only, but the backup still kept failing.

I finally stumbled upon this post from the Seagate website itself.

Per the article, I deleted the offending file from the backup drive and restarted the backup. It is now working again.