If you ever get a disk or disk image that will not unmount, you can force it with a Terminal command. Run Terminal and use “df” to list the drives. Find the one you want to unmount, such as /dev/disk3s2. Then use “diskutil unmountDisk force /dev/disk3s2″ to force it to unmount.
Related: Copying a Disk Image onto a HD, Classic OS Disk Images made usable with Snow Leopard, Secure erasing an old floppy disk and hard disk drive., Forced Quit didn’t work!, Using a game without the disk.

Cheers for that!
and it works. cool. no more violent ejections.
Awesome tip, worked like a charm – thanks!