maybe you haven't add SCSI-Emulation to your kernel?
I had the same problem until i added hdX=ide-scsi (X for your burner) to my grub menu.
Even if run as root it cannot modify permissions of something and fails with error message that it cannot find generic device. Also even in /dev/cdrom entry exists in fstab it adds entry for /dev/scd0. In result when K3b is run it cannot detect any devices.
maybe you haven't add SCSI-Emulation to your kernel?
I had the same problem until i added hdX=ide-scsi (X for your burner) to my grub menu.

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