Assuming You are not trying to use DVD map in your "CD drive only Mk3 navigation computer"
, so...
Always burn that image at
THE LOWEST burn speed possible! You ussually cannot chose 1x speed on latest DVD burners but 2,4x. It is OK, use this speed. If You do, then...
Consider that maybe the problem is not in the way You burn the DVD image, maybe You have:
- Mk4 firmware older than 10.00 (SW 4-1/00) that does not support dual layer DVDs (
honestly, I never tested DL DVD disks with older than 10.00 FW version - it may work though)
- dirty/poor condition DVD drive laser diode in Your Mk4 nav-computer (
I had bad one.
It read single layer DVDs reliably but DVD+-RW and dual layer with lots of errors or Please wait... messages. I replaced that Mk4 for another one that has now no problem even with DVD+-RW disks - disks with least reflection.
)
To solve the problem You can follow these steps (from cheapest to most expensive):
1) update to FW version 10.00 to get DL support
2) clean Mk4 DVD laser diode
3) replace Mk4 DVD laser diode
4) 
replace Mk4 navigation computer
Hope it will help a bit.