I made a backup of my NavTeq BMW 2006/02 (north America) disc as follows:
Grabbed the ISO using "Magic ISO" and saved to an NTFS partition.
Burned the ISO with
Nero v.7x to a LiteOn Internal writer on 4x speed. One copy to DVD+R (Maxell), one to DVD-R (Verbatim), both work flawlessly... no noise, no lost features and no problems on startup.