If you are using a safety backup of the nav DVD, ensure that your backup disc is of the highest quality. Non-knockoff Taiyo Yuden DVD+R discs burned with booktype set to DVD-ROM would be the premier choice.

Low-quality DVD blanks are hard to read by DVD drives not made to read writable discs, such as the Nav unit DVD drive.

 

Thats probably the problem, its a copy of his disk and its burned onto HP blank DVDs. He said those were the best kind to use as they were the easiest to read but i guess not...