DVDSP dual layer disk error(s) - will burn to drive but not to disk

Hi,

I've been trying to trouble shoot this issue for 2 days now. I feel like I've read every forum, watched every video and no solutions are availing themselves.

Production was edited in FCP7
I've authored a DL disk in DVDSP.
It has 2 video layers that share the same audio track. (I've done this before and there wasn't an issue - one video layer is a multi-cam edit, the other layer is a static wide)
Each video layer is approx 100 minutes.
I've exported both video files from FCP, multiple times to make sure the GOP structure matches.
Other items on the disk are simple a small slideshow, and some simple menus. (take up little space)

I've been able to successfully follow instruction to set my own breakpoints and have been able to build and format the production to hard drive. But when I try to burn the .img file using Toast to disk it fails and says: MEDIUM ERROR Sense Code = 0x73, 0x03

When I try to build it in DVDSP I get: Unknown device error (0x09, 0x01) - to which it was suggested that I try different media, I have... same problem exists.

It has been suggested that maybe my burner is dead - yet I can still burn DVD-5 just fine.

Though DVD-9 can hold up to 8.5gb, my assets total only 7.5 leaving plenty of room to build.

Any advice you can give would be key. This isn't the first time I've built a DL DVD in this program, but it's the first time I've ever had these issues.

Much appreciated...

Computer specs:
MacBook Pro 2.3Ghz Intel i7
8GB DDR3 ram
Exported from FCP 7
DVDSP 4.2.2

Files are all housed on a Thunderbolt external drive.

Cory Reeder
www.renaissancemanprod.com

On the Mac, you should be using DVD+RDL disks.

Cheers
Alexander