I am having a similar problem. I just performed a knoppix harddrive install. everything Works except for my cd-rom drives. I cannot mount either dvd or cdrw device.

Here is my fstab:
# /etc/fstab: filesystem table.
#
# filesystem mountpoint type options dump pass
/dev/hda1 / ext3 defaults,errors=remount-ro 0 1

proc /proc proc defaults 0 0
/dev/fd0 /floppy vfat defaults,user,noauto,showexec,umask=022 0 0
usbdevfs /proc/bus/usb usbdevfs defaults 0 0
sysfs /sys sysfs defaults 0 0
/dev/cdrom /cdrom iso9660 defaults,ro,user,noexec,noauto 0 0
/dev/cdrom1 /cdrom1 iso9660 defaults,ro,user,noexec,noauto 0 0
/dev/dvd /dvd iso9660 defaults,ro,user,noexec,noauto 0 0
/dev/cdaudio /cdaudio iso9660 defaults,ro,user,noexec,noauto 0 0
# Added by KNOPPIX
/dev/hda2 /mnt/hda2 auto noauto,users,exec 0 0
# Added by KNOPPIX
/dev/hdb1 /mnt/hdb1 ntfs noauto,users,exec,ro,umask=000 0 0


And here is what dmesg|grep sr returns:
matt@va-10:~$ dmesg|grep sr
Attached scsi CD-ROM sr0 at scsi0, channel 0, id 0, lun 0
Attached scsi CD-ROM sr1 at scsi0, channel 0, id 1, lun 0
sr0: scsi3-mmc drive: 20x/48x cd/rw xa/form2 cdda tray
sr1: scsi3-mmc drive: 40x/40x writer cd/rw xa/form2 cdda tray


I have no clue what is wrong. Help always appreciated.