I'm using Memorex +R dl's and book type set to DVD-ROM. When Nero does a verifly there are no errors. I'm stumped.

I've only used Verbatim DVD+R DL and never had a problem FWIW. I also use Nero 6.6.1.4

Try using ImgBurn.

Also, I have tried the TCH's NAV disc in a Prius and the older Prius DVD drives (ones under the seat) took forever to read it and then most failed. The same disc in a TCH worked fine. I also have not had any luck getting the Lexus 7.1 disc to work in the TCH yet...although I haven't tried that hard...the DL discs just get expensive after awhile....

I have used Verbatim DVD+R DL and RiData DVD+R DL. It ends up being dependent on what your burner likes best. But you don't have that problem since you are able to burn disc.

The only thing I can think of where ImgBurn might help is sometimes Nero does not do well with layer breakpoints. ImgBurn seems to come up with a decent one. You can also use it to create the original ISO so it will attempt to use the same layer breakpoint as the original disc.

Using Nero I did NOT do a disk to disk copy. Rather I created a Nero IMG backup file and then burned a Verbatim DVD+R DL from the IMG file BookType DVD-ROM.
This 7.1 copy also worked in a 2007 Lexus RX350 Nav.

I think I got a bad Lexus 7.1 disc.

There must be something unique about Prius DVd reader or my original disk that can't be copied. After pulling the battery cable I put one of the disks in I made including a direct copy and they all say loading and they all load. Unfortunatly after they load it says "unable to read data, check if map disk is correct". I bought a 7.1 gen 5 disk off Ebay put it in and it says "loading do not turn off power". However it never loads. It goes from loading to vertical lines then back to loading but the loading line never gets past about an 1/8 of and inch. I have no idea what's going on.

I didn't think the Prius had the Hi-Res NAV that the Camry/Lexus have. If that's a Camry DVD you have that might be the issue?

Yes, that is true last I knew but that might have changed with the 2005+. I know my buddy who has a 2004 Prius could not get the Camry DVD to work. It would read forever and then fail.

My original disk is a U40 464210-0701 Ver. 5.1 and even direct verified copy of it won't work. There my be some kind of security on the disk that doesn't copy. The Ebay disk loads forever then fails. The disks I made load, but then say " Unable to read data, check if map disk is correct". Any ideas?

It's just not burning right. Not sure what to tell you. If the Ebay disc loads forever and fails, I suspect the new Prius cannot handle the Camry DVDs. I cannot confirm this as I do not have a Prius.