Writing to DVD-RAM is causing me grief.
For testing I've been using a purpose built Gentoo system, X64, Phenom II CPU (3 cores).
The MB uses the AMD SB700/SB800 AHCI chipset.
I have installed a PCI-e AHCI controller with a JMicron chipset to confirm its not chipset related.
The drive is a new LG model. I've tried a older LG and an old Asus.