could I ask exactly what you are doing!! My method with nero is as follows - I make a folder on the hard drive called copy - I then dump everything I wish to burn into that folder - when ready I run nero and simply drag and drop the copy folder into nero - I have never had any problems. If you do not have a lot of memory have nothing else running while nero is at work.
not having any probs but Nero site not giving any info for 5.5 updates it's all for selling V6 at present.
Mary/Earthangel, drop the write speed as suggested, and check not trying to write faster than disc's allow even though default settings should prevent this, also may want to check files you are wanting to copy are OK. Only time I have had a duff write is when a file was corrupted that I was trying to copy.