Does anybody have any experience with backing up the navigation dvd's? Since they are so expensive I wanted to make a backup copy. I bought an HP dual layer DVD+R 2.4 speed disc and made the backup. The system successfully booted up but then continuously gave me 'unable to read disc' errors, so it seems not to like the HP media.

Has anybody tried Verbatim, Memorex, or anything else that worked better?

My car is a 330ES.