Very odd. What is the make and model of your dvd burner?
You can try another burning program and see if it is just Nero being its usual worthless self.
I recommend ImgBurn, which is a free burning program located here: www.imgburn.com
If you are used to the interface in Nero, you may not like this program at first as it is quite different. To erase a disk with it, put the dvdrw or cdrw disk in the drive and click on the red button on the main screen. I'm posting a screenshot below.