also a quick google search turned up this excerpt from a videohelp.com page.
By the way guys, I think I figured out why RecordNow 7.3 sometimes refuses to burn VIDEO_TS structures (formatting errors) of the seemingly OK commercial DL discs. At least in my latest backup attempts it happened on a few DL discs of "Poirot - The Complete Series" Region 2 (UK). It's because of the Parallel Track Path (PTP), which is not compatible with Opposite Track Path (OTP), used in DVD+R DL format. You can pretty much check with any decent DVD information tool if the disc is OTP or PTP. Most pressed DVD9's are OTP (the same as DVD+R DL), but some are still PTP and that could be bad news, to a point.
With PTP discs that I tried to backup, the second layer was larger than the first, which cannot be with OTP. Therefore RN 7.3 had a good reason to refuse to burn it, because there was no place to put a layer break.
Now, if there were many more chapters or cells per title, it would be possible for RN 7.3 to choose one of those spots, but in "Poirot" case each chapter was about 15 to 20 minutes apart, with no new cells anywhere in between. When I did the ISO reading with DVDDecrypter, later I analyzed this ISO file with ImgBurn and it said that there was no valid layer break position that could be pulled off from IFO file. Of course I could attempt to burn it with DVDDecrypter or ImgBurn, but the result would surely be a permanent freeze somewhere in the middle if the DVD (because even ImgBurn reported that it can do nothing about the layer break). Therefore I had to experiment.
After some tests and thinking, my effective working solution, without doing a complete reauthoring, is to simply use DVDRemake Pro and in one of the titles close to the center point of the DVD (may take awhile to find it manually), in some relatively quiet spot simply make a cell split. Do not create a new program, but simply a cell split. Then burn this VIDEO_TS with RecordNow 7.3 and it should work, if you split it a little past the middle point of the DVD. For example, if you have a 7.2GB DVD, you want to find a spot somewhere between 3.6GB and 3.9GB to make a new cell. Though closer to 3.6GB mark would probably be better.
I did already a few of these stubborn PTP backups this way and they all burned and played perfectly, without any need to re-author. RecordNow inserted the IFO layer break information precisely to the cell that I split between the long chapters. Hopefully this will help those of you who get frequent formatting errors on backing up PTP DL discs.