Question about "Errors on Disc"

I use Windows, as least I think it's Windows, "Disc Copier" to burn discs. Every once in a while, the disc pops out and I get an on screen message indicating "there were errors in the recording process." So, I pop in a new blank disc and begin the burning process over agai. My question is, if this happens to any one else, are these discs defective and can they be returned, or is this operator error, or what? Thanks.