if you can't unmount usb flash through gui. - read this

[4est]

if your usb gets mounted, but you can't unmount it using any guis (xfce kde etc) and you get an error message like
can't unmount, bla bla was already mounted from the command line.

check out (if you have it)
/etc/udev/rules.d/10-local.rules

which calls
/usr/local/bin/mount-device.sh

I renamed the /usr/local/bin/mount-device.sh to /usr/local/bin/mount-device.sh.old

and now I can umount my usb flash drive using file managers icons etc.
I guess I don't even need the /etc/udev/rules.d/10-local.rules to begin with.