I'm running kubuntu with kde 4.5.4

If I insert a USB memory stick nautilus starts up OK, if I hit
the eject button for the device in the left panel, it is unmounted
OK.

However, if I close down nautilus, then use the device notifier
to eject(unmount) the device it fails with the message -
"Could not unmount....One or more files are open....
But, I can unmount the device using the "umount" command.
Clearly, no files are left open and the device notifier has
got it wrong.

Is this a bug?

If after waiting a few moments for any process close downs to complete it still refuses to eject, please try the steps at viewtopic.php?f=66&t=92239&p=183510#p183433 just change "solid-hardware mount" to "solid-hardware unmount" and see what error message it gives.

Did that. Error message is -

Error: org.freedesktop.Hal.Device.Volume.NotMountedByHal: Device to unmount is not in /media/.hal-mtab so it is not mounted by HAL

Another scenario:

If I run the solid-hardware unmount command while nautilus is still accessing the USB memory stick, I get the same error message.
In addition the device notifier pops up with the Could not unmount the following device: message and the USB memory stick remains mounted and accessable in that nautilus window.

If I subsequently use umount on the command line to unmount while nautilus is still running on the root directory of the USB memory stick, it unmounts and nautilus terminates.

If I'm accessing a sub-root directory, nautilus doesn't terminate and the command line umount fails as you would expect.

While I have done a clean install I think at about 9.04, all the rest have
been upgrades, and my user home directory dates from 8.10.
Are there some user settings I need to clear without loosing my email, menu changes etc.?

Uh Oh. You need to contact your distribution regarding that, it could be that Nautilus is using UDisks already, which prevents the usage of the Device Notifier to unmount the disk in that case, until you upgrade to KDE 4.6.

OK. Reported, see

https://bugs.launchpad.net/kubuntu-ppa/+bug/695539

My work around is to remove nautilus.

Doesn't fix the problem, just stops me
from stumbling across it.