I've had one or two faulty burns using Nero, and finally worked out why. I am normally doing several thing at the same time for example listening to music,redubbing a video,browsing web sites,while burning a DVD. 
That is when I get failures. The compuyer is reading and writing to the hard disks for several programs at the same time and some data corruption occurs.
When I burn with only Nero running there is no problem.