Wait ... have you ejected the CD yet?
Perhaps try these various methods of ejecting and then reinsert the media and see if it mounts on its own..
3 ways to eject a CD on a Mac.
1. Drag to trash (not possible in this case).
2. Hit eject button on keyboard -- try quitting all apps first (apparently not working in this case?).
3. Reboot, and hold down your mouse button during reboot. This is your failsafe.
Hope this helps?