Reboot after burning:
In certain cases, some burning devices do not change back to the "Ready" state after the burning is done. If that happens the computer needs to be restarted after the burning process of large amounts of data (DVD).
If a DVD/CD does not play or work after you have burned the medium, choose another medium type or brand and repeat the burning process. Eventually, you may have to lower the burning speed. Many devices are not compatible with cheap or old media (blanks). The quality of some blanks is actually so bad, that the specified maximum speed cannot be reached in most cases.
VideoDVDs, especially RW Media may not be recognized by some DVD player the first time you insert the DVD. In those cases, simply re-insert the medium in the DVD player.
A number of errors of burning devices are errors in the so called firmware. This is a small software package built into the device, sometimes also known as the driver. Many manufacterers offer a firmware update to resolve those problems. Contact the manufacturer of the device and ask if there is an update available (or visit their website).