Try burning something with a different burning program and see if it is a problem within Nero.
ImgBurn is free to use and well respected in these forums. www.imgburn.com
Set burning speed to a moderate speed, say 8 or 12x when using 16x media.
If it fails, post the failed log here in your thread. You can find the ImgBurn log by clicking Help-->ImgBurn Logs.