If you check the dates on the first two posts in this thread, you'll notice that you've resurrected a thread from a couple of weeks ago. For best results I'd recommend that you start a new thread for your question.
The most common causes of DVD writing problems are using poor quality media and/or using media that your hardware just doesn't like. We generally recommend Verbatim or Taiyo Yuden media.
Oh, and welcome to CDFr... MYCE