I got this problem and it turned out to be a bad kdeinit
I managed to solve it without restarting KDE by following these steps:
lsof | grep /mnt/cdrom
Close anything I can that is accessing it such as the instance of Konsole I just used.
kill <PID instance of offending kdeinit process>
The PID you want is the second column beside the kdeinit
instance that lsof gave you.
On my system, there were several kdeinit
instances and killing just the offending one didn't cause any problems. Then manually unmount the CD and everything is back to normal. I'm on a relatively unmodified Mandrake 10.0 install.