Have you downloaded new content from Store when this started to pop up? I've understood that some of the content may cause some problems and corrupt the ccmerged file in your DCBackup folder and because it's also linked to store content, it might has something to do with this.
You might want to try fix / download clean ccmerged file, instructions: https://nonasims.wordpress.com/2012/05/17/dcbackup-ccmerged-package-and-your-premium-content-items/ and see if that will fix the problem. Easy way is to download the ccmerged file from the link (last Q-part in the main article) and replace the old one with it in your DCBackup folder.
I've had a lot of problems in past with store content but this clean ccmerged file solved them all.