Acquisition not started after creation of new project

In luciole 0.9.2, after creating a project , with new project assistant. The acquisition doe not start in 'ACQUISITION' mode. A webcam is used.
The message libv4l2: error setting pixformat: Périphérique ou ressource occupé. is displayed
Luciole is in an inconsistent mode --> not usable.
If luciole is closed, then re-opened, the new created is loaded correctly in luciole

and exception traceback message :
Traceback (most recent call last):
  File "/home/nico/dev/luciole-repo/luciole/luciole/ctrl/load_rush.py", line 135, in _on_timeout
    self._on_rush_finish(_qmsg['finish'])
  File "/home/nico/dev/luciole-repo/luciole/luciole/ctrl/load_rush.py", line 165, in _on_rush_finish
    self.emit("rush-loaded",rush_obj )
  File "/home/nico/dev/luciole-repo/luciole/pitivi/signalinterface.py", line 145, in emit
    *args, **kwargs)
  File "/home/nico/dev/luciole-repo/luciole/pitivi/signalinterface.py", line 119, in emit
    res = cb(*ar, **kw)
  File "/home/nico/dev/luciole-repo/luciole/luciole/ctrl/ctrl_project.py", line 469, in _rush_load_finish_cb
    self._terminate_project_load(rush_obj)
  File "/home/nico/dev/luciole-repo/luciole/luciole/ctrl/ctrl_project.py", line 496, in _terminate_project_load
    self.emit('project-loaded', self.project )
  File "/home/nico/dev/luciole-repo/luciole/pitivi/signalinterface.py", line 145, in emit
    *args, **kwargs)
  File "/home/nico/dev/luciole-repo/luciole/pitivi/signalinterface.py", line 119, in emit
    res = cb(*ar, **kw)
  File "/home/nico/dev/luciole-repo/luciole/luciole/ctrl/base.py", line 65, in project_loaded_cb
    self.prepare(project)
  File "/home/nico/dev/luciole-repo/luciole/luciole/ctrl/ctrl_acq.py", line 107, in prepare
    self.emit('acquirer-ready')
  File "/home/nico/dev/luciole-repo/luciole/pitivi/signalinterface.py", line 145, in emit
    *args, **kwargs)
  File "/home/nico/dev/luciole-repo/luciole/pitivi/signalinterface.py", line 119, in emit
    res = cb(*ar, **kw)
  File "/home/nico/dev/luciole-repo/luciole/luciole/ctrl/ctrl_project.py", line 513, in _acquirer_ready_cb
    self.acquisition_mode()
  File "/home/nico/dev/luciole-repo/luciole/luciole/ctrl/ctrl_project.py", line 197, in acquisition_mode
    self.ctrl_acq.start()
  File "/home/nico/dev/luciole-repo/luciole/luciole/ctrl/ctrl_acq.py", line 149, in start
    self._pipeline.play()
  File "/home/nico/dev/luciole-repo/luciole/pitivi/pipeline.py", line 297, in play
    self.setState(STATE_PLAYING)
  File "/home/nico/dev/luciole-repo/luciole/pitivi/pipeline.py", line 277, in setState
    raise PipelineError("Failure changing state of the gst.Pipeline to %r, currently reset to NULL" % state)
pitivi.pipeline.PipelineError: Failure changing state of the gst.Pipeline to <enum GST_STATE_PLAYING of type GstState>, currently reset to NULL