Disk images suddenly will not unmount.

Question

One of several intermittent troubles I am having on my new 24" iMac with Leopard:
suddenly when using disk images none will unmount. Only launching Disk Utility and unmounting them there works. Or logging out of my account. The eject symbol next to the disk image's name doesn't work. Dragging the disk image to the trash doesn't work either. If I have a disk image open and click eject it's Finder window closes, but he disk image remains mounted.
Three wipes of the HD and reinstalls of Leopard have failed to fix this issue.

Answer 1

I've got this one too. It also happens with external drives and not just disk images.
I made a little apple script which ejects disks and disks images.
on open some_items
repeat with this_item in some_items
try
do shell script "hdiutil detach " & quoted form of POSIX path of this_item
end try
end repeat
end open
open the above in Script editor and save it as an application. Put this application (or an alias to it) on the desktop. To unmount one or more disks drop them onto this application (you can do it with several disks at once). I find that this works a bit faster than launching disk utility and ejecting the drives manually. Still, it would be preferable if they just fixed it.