cdrom does not un-mounts

["J.S.Sahambi" <jsahambi@iitg.ernet.in>]

I am using Debian/sid. Some times when I mount a cdrom and try to 
unmount it immediately, it gives the following error on the terminal:

umount: /cdrom: device is busy
umount: /cdrom: device is busy

But the fact is the cdrom is not being used by any of my terminals or 
programs (as I have not used the terminal or any program to browse or 
use the cdrom). The only way I have found to umount the cdrom in this 
case is to logout (or kill the xserver with ctrl-alt-backspace) and 
login are root or same user and unmount. Then the cdrom unmounts with 
out any problem.

Can anybody shed some light on it.

Thanks
JSS