I have had this with Nero too,i also did not find anything wrong with the setup or the copies i did but they still jumped and the sound was off or not there,and from someone on here i tried this click here and i have to say it does the job a lot better than Nero,takes a bit longer but the result is better.
Under video sttings you can choose high quality and also 2 pass for the bit rate . Though you may find that burning at the lowest speed sorts it out . What was the original format off your files . Personally I'd use Flick as suggested
Ok run your file through nero again but dont choose burn choose create hard disc folder . Once you have that play that back and see if that is ok if it is then its possibly the burn process either your writer or media. let us know what happens.If its good you can then choose to try and burn it with something better than nero