USB Creator unknown filesystem type 'iso9660'

Cuando arranco usb-creator-gtk o usb-creator-kde me da el error "Installation failed" y no me crea el USB con Trisquel. Me funciona perfectamente en una instalación limpia de Trisquel pero esta es una versión que ha pasado por dos upgrades. Esta es la bitácora de USB Creator

cao@cao-estacion:~/Escritorio$ tail -n45 ~/.cache/usb-creator.log
usb-creator 2011-07-27 03:17:46,799 (DEBUG) uiparser.py:62: pop layout QGridLayout gridLayout
usb-creator 2011-07-27 03:17:46,800 (DEBUG) uiparser.py:68: pop widget QDialog Dialog
usb-creator 2011-07-27 03:17:46,800 (DEBUG) uiparser.py:75: new topwidget None
usb-creator 2011-07-27 03:17:47,079 (DEBUG) backend.py:59: detect_devices
usb-creator 2011-07-27 03:17:50,139 (DEBUG) backend.py:84: device_added: /org/freedesktop/UDisks/devices/sdb1
usb-creator 2011-07-27 03:17:50,171 (DEBUG) backend.py:132: partition added: /org/freedesktop/UDisks/devices/sdb1
usb-creator 2011-07-27 03:17:50,197 (DEBUG) backend.py:138: id-type: vfat
usb-creator 2011-07-27 03:17:50,205 (DEBUG) backend.py:144: id-label:
usb-creator 2011-07-27 03:17:50,290 (DEBUG) backend.py:165: mount: /media/4519-E7E4
usb-creator 2011-07-27 03:17:50,292 (DEBUG) frontend.py:234: add_target: /org/freedesktop/UDisks/devices/sdb1
usb-creator 2011-07-27 03:17:50,359 (DEBUG) backend.py:84: device_added: /org/freedesktop/UDisks/devices/sdb
usb-creator 2011-07-27 03:17:50,397 (DEBUG) backend.py:184: disk added: /org/freedesktop/UDisks/devices/sdb
usb-creator 2011-07-27 03:17:50,434 (DEBUG) frontend.py:234: add_target: /org/freedesktop/UDisks/devices/sdb
usb-creator 2011-07-27 03:17:50,435 (DEBUG) backend.py:84: device_added: /org/freedesktop/UDisks/devices/dm_2d1
usb-creator 2011-07-27 03:17:50,468 (DEBUG) backend.py:84: device_added: /org/freedesktop/UDisks/devices/sda
usb-creator 2011-07-27 03:17:50,500 (DEBUG) backend.py:84: device_added: /org/freedesktop/UDisks/devices/sda1
usb-creator 2011-07-27 03:17:50,549 (DEBUG) backend.py:84: device_added: /org/freedesktop/UDisks/devices/sda2
usb-creator 2011-07-27 03:17:50,606 (DEBUG) backend.py:84: device_added: /org/freedesktop/UDisks/devices/dm_2d0
usb-creator 2011-07-27 03:17:50,658 (DEBUG) backend.py:84: device_added: /org/freedesktop/UDisks/devices/sda5
usb-creator 2011-07-27 03:18:13,072 (DEBUG) backend.py:22: Backend told to add: /home/cao/ISOs/trisquel_4.5.1_i686.iso
usb-creator 2011-07-27 03:18:13,073 (DEBUG) misc.py:128: ['isoinfo', '-J', '-i', u'/home/cao/ISOs/trisquel_4.5.1_i686.iso', '-x', '/.disk/info']
usb-creator 2011-07-27 03:18:13,207 (DEBUG) frontend.py:274: add_source: /home/cao/ISOs/trisquel_4.5.1_i686.iso
usb-creator 2011-07-27 03:18:17,888 (DEBUG) backend.py:262: install source: /home/cao/ISOs/trisquel_4.5.1_i686.iso
usb-creator 2011-07-27 03:18:17,889 (DEBUG) backend.py:263: install target: /org/freedesktop/UDisks/devices/sdb1
usb-creator 2011-07-27 03:18:17,890 (DEBUG) backend.py:264: install persistence: 128
usb-creator 2011-07-27 03:18:26,487 (ERROR) frontend.py:204: Installation failed.
Traceback (most recent call last):
File "/usr/lib/pymodules/python2.6/usbcreator/frontends/kde/frontend.py", line 426, in install
allow_system_internal=self.__allow_system_internal)
File "/usr/lib/pymodules/python2.6/usbcreator/backends/udisks/backend.py", line 294, in install
source = self.helper.MountISO(isofile)
File "/usr/lib/pymodules/python2.6/dbus/proxies.py", line 140, in __call__
**keywords)
File "/usr/lib/pymodules/python2.6/dbus/connection.py", line 620, in call_blocking
message, timeout)
DBusException: org.freedesktop.DBus.Python.usbcreator.misc.USBCreatorProcessException: Traceback (most recent call last):
File "/usr/lib/pymodules/python2.6/dbus/service.py", line 702, in _message_cb
retval = candidate_method(self, *args, **keywords)
File "/usr/share/usb-creator/usb-creator-helper", line 176, in MountISO
popen(['mount', '-o', 'loop', device, ret])
File "/usr/lib/pymodules/python2.6/usbcreator/misc.py", line 143, in popen
raise USBCreatorProcessException(err)
USBCreatorProcessException: mount: unknown filesystem type 'iso9660'