I own a PowerBook G4 laptop... I successfully burned about 5 DVDs using DVD Backup, DVD2oneX, and Toast 6. I had problems burning with Memorex Discs when I bought them in bulk (Error message: "Could not record because there is a problem with the source material. Result Code = -18774.") After reading some of these forums I found people had similar problems with Memorex discs bought in bulk. I returned the Memorex discs and bought 50 Fuji DVD-R. I AM STILL GETTING THAT SAME ERROR MESSAGE. I'm really frustrated now. Can anyone help? Thanks!