/dev/cdrom /mnt/cdrom auto noauto,owner,ro 0 0
The first auto means the filetype is selected automatically. You might try using "iso9660" and see if that helps. The second "noauto" means that this line is ignored during bootup when the system runs "mount -a". You want this option for all removable media, because if a disc or usb pendrive isn't present, it can't be mounted and would cause the bootup to fail. Consider the possibility that the disc or drive is bad.
What kind of disc are you trying to mount. You don't mount music cd's. A program like xmms plays the disc from the raw device /dev/cdrom.