Version:            (using KDE 4.2.90)
OS:                Linux
Installed from:    SuSE RPMs

1. Put cd in cdrom
2. Open cd contents in dolphin
3. Rightclick on the cdrom item on the dolhin's left panel

Error message appears at the bottom saying 
org.freedesktop.Hal.Device.Volume.Busy: umount: /media/cdrom: device is busy

This is good information, but I can't do much with it - the device might be opened in some other program (another dolphin instance, krusader or in console) and I can't guess in which one. Even worse, if this program does not have gui, or already closed, but by some reason did not release the media (sometimes this also happens, don't know why - probably this might be easier to reproduce if cd is scratched).

fuser -km /media/cdrom console command or forced/lazy umount might help in this case, but this would be >>much<< better in dolphin provided gui for that - especially for users, who does not know anything about this commands. Personally for me this is one of the most annoying linux problem, which lives for years - I remember the situations when I even had to reboot just to release my disk.

So, along this this error message, dolphin could show a number of buttons to take actions which could help in this case to release the media - like:
1. Go to application, which locks device
2. Kill application, which locks device
3. Force umount media
4. Lazy umount media
etc