what version of nero were you using?
i had issues with nero and it turned out to be my dvd writer.
i didn't think it was, becuase other software was working still, but very soon they stopped working. completely. to be honest, i've used roxio in the past and wasn't all too impressed. just didnt like the layout really. nero is quick, easy, does what i want it to and does it easy enough. then again, if it works for you, then its good. after all, all it has to do is put the files to dvd/cd blu-ray or hd-dvd (if you're rich enough)
i've bought a new dvd writer, a lovely sata one too

works fine with nero.
but yeah, try out some other programs and if you keep getting rejected burns, it might be a problem with your actual dvd writer.