...i read through the v29.1 NAV OS thread (wow...all 34 pages!!!). The OS disc errors were resolved using Alcohol120%. Burned correctly now.

As for the v2007.2 NAV Disc backup, your DVD Burner needs to have a bitsetting or booktype setting to switch a DVD+R to burn as a DVD-ROM. That's the format with which the MKIV NAV Disc drive is compatible.