Can not mount /dev/loop1 on /cow (when persistence)

[Fabio Marconi]

Hello
Testing beta1, using usb-creator from Oneiric this error only appear if the 'creation of persistence file' option is selected.
Without that, everything works.
Valgrind attached
Apport seems started with exception not captured Errno2 popup.
Thanks
Fabio

ProblemType: Bug
DistroRelease: Ubuntu 11.10
Package: usb-creator-gtk 0.2.31.2
Uname: Linux 3.0.0-0300rc7-generic x86_64
Architecture: amd64
CheckboxSubmission: da0a9053457cd51534683f0d3b1afbb3
CheckboxSystem: 4ed15c40009aa6f7770f606350a390a2
Date: Wed Aug 31 22:55:53 2011
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Alpha amd64 (20110318)
PackageArchitecture: all
ProcEnviron:
 PATH=(custom, no user)
 LANG=it_IT.UTF-8
 SHELL=/bin/bash
SourcePackage: usb-creator
UpgradeStatus: Upgraded to oneiric on 2011-08-28 (3 days ago)

[Brian Murray (brian-murray)]

From the USBCreatorLog files:

usb-creator 2011-08-31 22:47:54,627 (DEBUG) install.py:309: create_persistence
usb-creator 2011-08-31 22:47:54,635 (DEBUG) misc.py:129: ['dd', 'if=/dev/zero', 'bs=1M', 'of=/media/D320-9BE6/casper-rw', 'count=1024']
usb-creator 2011-08-31 22:49:28,302 (DEBUG) misc.py:129: ['mkfs.ext3', '-F', '/media/D320-9BE6/casper-rw']
usb-creator 2011-08-31 22:49:29,481 (ERROR) install.py:147: Exception raised:
Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/usbcreator/install.py", line 143, in run
    self.install()
  File "/usr/lib/python2.7/dist-packages/usbcreator/install.py", line 583, in install
    self.create_persistence()
  File "/usr/lib/python2.7/dist-packages/usbcreator/install.py", line 330, in create_persistence
    popen(mkfs_cmd)
  File "/usr/lib/python2.7/dist-packages/usbcreator/misc.py", line 139, in popen
    startupinfo=startupinfo)
  File "/usr/lib/python2.7/subprocess.py", line 679, in __init__
    errread, errwrite)
  File "/usr/lib/python2.7/subprocess.py", line 1239, in _execute_child
    raise child_exception
OSError: [Errno 2] File o directory non esistente