It seems like the disk drive is trying to open the wrong device.
1. Check in devices tree that device for the Disk Drive is set to /dev/hdc
2. Check using dmesg | grep hdc that the DVD drive is present
3. Look in /var/log/pluto/26_Disk_Drive.log and see the following:
Error: couldn't open /dev/hda.
Funnily enough, if I move the IDE cable so that the disk is /dev/hda, then I get an error in the Disk Drive log saying /dev/hdc can't be opened!
I must be doing something really stupid here. Can anyone suggest what?