The Apple branded DVDs should work as they are rebranded Verbatim discs. If cleaning the drives doesn't work, it is possible the PRAM battery needs replacing on the Macs in question that 4 or more years old. See my FAQ*: http://www.macmaps.com/cdrfailure.html
If you have some old DVDs, it is possible the environment they were in were not suitable for burning after a period of time.
The Blank discs are fine. I am very meticulous. I've also zapped my Pram and this also makes no difference.
I spoke to a tech at Apple this AM and he agreed that there is a software problem with the OS and he offered no solution.
The drive will recod CDRs however.
I think Apple wrote my laptop out of the OS and they don't care.
Love you to Apple.
8 Macs and close to $24,000 invested and this is the love I feel.