Comment 8 for bug 982430

I don't see any changes to this part of the installer *at all* - not just no relevant changes, cdrom-detect.postinst and the Linux variant of list-devices literally haven't changed at all. Maybe a udev or kernel change?

list-devices is probably the easiest place to start debugging; I expect you'll find that on 11.10 the virtual CD is showing up in /sys/block/ and has an ID_CDROM= entry in its 'udevadm info -q env' output, while on precise either it's missing from /sys/block/ (perhaps kernel bug, perhaps some necessary module not being properly delivered to the installer) or it doesn't have an ID_CDROM= entry (probably a udev bug). It'd be helpful to narrow this down.