I had the same problem (error) of "Startup Disk Creator" (Xubuntu 15.10).
And the tool 'gnome-disks' (from the package 'gnome-disk-utility') helped me:
apt-cache search gnome-disk
gnome-disk-utility - manage and configure disk drives and media
which gnome-disks
/usr/bin/gnome-disks
Use the "Restore Disk Image..." from a disk Menu.
I had the same problem (error) of "Startup Disk Creator" (Xubuntu 15.10). disk-utility' ) helped me: gnome-disks
And the tool 'gnome-disks' (from the package 'gnome-
apt-cache search gnome-disk
gnome-disk-utility - manage and configure disk drives and media
which gnome-disks
/usr/bin/
Use the "Restore Disk Image..." from a disk Menu.