I wonder what software you have got installed on your machine - it's possible something is interfering with the burn process.
It may be helpful to post a log of one of your burns in Nero, which, amongst other things, gives this information. Use the Save Log... button at the bottom of the burn window. You can open the file in a text editor, then cut and paste the text file into a reply, omitting the top two or three lines that contain your name and Nero serial number.
Obviously, if you have any, it may be better to use rewriteable media for this test so that you don't waste another disc. Trying rewriteable media may also show whether or not it's a media problem.