Movie burning problems

I have been downloading movie files under 700 MB and burning them to a CD-R with Nero Burning rom for months with no problem. Now lately about every 3rd burn or so is bad. it burns nero says successful, but when I go to play there is no file. The size is gone, but no visable file to explore. It seems to be too frequent for your occassional “bad disk in the pack” and I have also tried switching brands. I have a sony liteon DVD burner and have no problems with making audio cd’s just making video cd’s. Anybody have any thoughts? Don’t have any dvd disks so i don’t know if that is working right. Thanks so much