Hi
You have to set dvd+r dl media to booktype ROM. This is to ensure (about 90%) that your player will play it back. You can set booktype by using the official liteon tool or just set the drive to autoset booktype rom by using omnipatcher from codeguys. Booktype setting only applies to dvd+r's and there are no such thing as dvd-r dual layer media (atm).

regards