Comment 23 for bug 37768

Some more on this bug...just another account of it:
gnome-volume-manager tries to mount partitions currently being formatted by GParted causing GParted to quit formatting and give an error.

Steps to reproduce:

1) Insert USB drive/thumbdrive (presumably any partition will work, whether internal or external)
2) Watch it mount in Nautilus (if gnome-volume-manager set to automount drives)
 then right-click it in the Places menu and select "Unmount"
3) Open GParted and select that disk/partition.
4) Delete current partition(s) then create a new partition and begin the format.

If gnome-volume-manager is set to automount by selecting "Mount removable drives when hot-plugged"
 it will try to mount the new partition while GParted is still trying to create it, causing
 GParted to quit and give an error:

"GParted 0.2.5

Delete /dev/sdb1 (fat32, 1.91 GiB) from /dev/sdb ( SUCCES )

========================================

Create Primary Partition #1 (fat32, 1.91 GiB) on /dev/sdb ( ERROR )

create empty partition ( SUCCES )

path: /dev/sdb1
start: 34
end: 4000184
size: 1.91 GiB
set partitiontype ( SUCCES )
create new fat32 filesystem ( ERROR )

mkdosfs -F32 -v /dev/sdb1

mkdosfs 2.11 (12 Mar 2005)
mkdosfs: /dev/sdb1 contains a mounted file system.

========================================"

This is important because gnome-volume-manager's default action is to automount removable drives.
I have offered advice many times on Ubuntuforums.org to people experiencing this problem. The quick fix is to
disable automounting when using GParted.