try this one
u just see that urs /mnt/cdrom is properly pointing to the device .all the device can be see as hda(hard disk generaly),hdab(secoind hard disk if any), or hdc(cdrom).
after that also see the entry in /etc/fstab.
u can do all these thing on command promt or linuxconf from the graphical mode.
hope after checking these thing u'll be able to fix it.
bye enjoy linux world