What brand,rate,and format was your backup disc?
How fast did you burn that backup?
Brand and model# of your dvd burner?
Since you are trying to copy your backups,high quality media,quality burner, and a sensible 4x burn speed helps.The cheap media and or too fast burn speed on your 1st backup may cause problems when trying to re-rip them.Weaker burners also have a harder time.
My high quality media,4x burn speed,benq 1620,and Nero express allow me to re-rip my backups with no coasters,about 15 minutes total process time at 4x.