At some point over the last few months my dvd drives stopped working on Linux Centos 5.0 (kernel 2.6.18). Having spent half the day googling to find a fix, looking at udev, hal, fstab, bios settings, ata/piix/ide modules, jumper settings on the drive... I found a fix to the problem. Having tried to execute
I got an error message about not understanding what the dma option is. Which led me onto editing /etc/modprobe.conf and commenting out the the line:
options ide-cd dma=1
This fixed the problem.