If i am not mistaken the software that you are using is Videopad and not Wavepad.
Have you tried different types of DVD discs or a different program to burn the DVD with?
Since the issue happens after you have burn the disc, you can try burning the video using another program like Express burn to confirm if the issue remains.
For further assistance you can also create a ticket with our technical support team through this link http://www.nch.com.au/support/index.html and select the option that says “I Need Technical Support”.