i have the same problems..
but i allways burn with the NEC 2510A firmware 2.18 until yesterday with the same media.
i don't have any problems before now.
i have try to upgrade my firmware on my NEC 2510A to firmware 2.19 including booktype patch
Booktype setting allows for setting the booktype of a +R/+RW and +R-DL DVD disc to DVD-ROM.
This improves compatibility for some older commercial players.
The booktype of minus media cannot be changed.
and now i can burn