Making a copy of a copy?

[SpyderBytes]

As most of us Dads here would know (if there are any?) making backups of Toy Story, Spiderman, Buz Light Year are a life saver. I made backups of all my sons DVDs and stowed the originals for future use. The other day he got into the cupboard and trashed one of the originals. Although I still have the backup I thought I'd copy the copy just so I had another ....well copy. Unfortunately my DVD burner won't even recognise the disc. It works in the DVD player ok. Does this mean I can't copy from a copy. maybe a trip back to the video store. Thanks for any help you can provide. Oh and using CloneDVD and AnyDVD. Generally use -r and don't have problems bar this one