$ bzr visualize
bzr: ERROR: exceptions.AttributeError: 'module' object has no attribute 'ProgressBarStack'

Traceback (most recent call last):
  File "/usr/lib/python2.5/site-packages/bzrlib/commands.py", line 729, in exception_to_return_code
    return the_callable(*args, **kwargs)
  File "/usr/lib/python2.5/site-packages/bzrlib/commands.py", line 924, in run_bzr
    ret = run(*run_argv)
  File "/usr/lib/python2.5/site-packages/bzrlib/commands.py", line 560, in run_argv_aliases
    return self.run(**all_cmd_args)
  File "/usr/lib/python2.5/site-packages/bzrlib/plugins/gtk/__init__.py", line 277, in run
    set_ui_factory()
  File "/usr/lib/python2.5/site-packages/bzrlib/plugins/gtk/__init__.py", line 105, in set_ui_factory
    bzrlib.ui.ui_factory = GtkUIFactory()
  File "/usr/lib/python2.5/site-packages/bzrlib/plugins/gtk/ui.py", line 195, in __init__
    self.set_nested_progress_bar_widget(ProgressBarWindow)
  File "/usr/lib/python2.5/site-packages/bzrlib/plugins/gtk/ui.py", line 224, in set_nested_progress_bar_widget
    self._progress_bar_stack = progress.ProgressBarStack(klass=widget)
AttributeError: 'module' object has no attribute 'ProgressBarStack'

bzr 1.16 on python 2.5.2 (linux2)
arguments: ['/usr/bin/bzr', 'visualize']
encoding: 'UTF-8', fsenc: 'UTF-8', lang: 'en_US.UTF-8'
plugins:
  bzrtools             /usr/lib/python2.5/site-packages/bzrlib/plugins/bzrtools [1.16]
  gtk                  /usr/lib/python2.5/site-packages/bzrlib/plugins/gtk [0.95.0.final.1]
  launchpad            /usr/lib/python2.5/site-packages/bzrlib/plugins/launchpad [1.16]
  netrc_credential_store /usr/lib/python2.5/site-packages/bzrlib/plugins/netrc_credential_store [1.16]
  push_and_update      /home/glyph/.bazaar/plugins/push_and_update [0.2dev]
  svn                  /usr/lib/python2.5/site-packages/bzrlib/plugins/svn [0.6.2]
*** Bazaar has encountered an internal error.
    Please report a bug at https://bugs.launchpad.net/bzr/+filebug
    including this traceback, and a description of what you
    were doing when the error occurred.