I'm working on a HUGE project (that is a little bit disordered, by the way :-)).

I KNOW that there are filenames that have strage characters.

I just tried bzr status and here's what happens (with bzr 1.6 b2):
$ ~/instaladores/bzr-1.6b2/bzr status
bzr: ERROR: exceptions.UnicodeDecodeError: 'utf8' codec can't decode bytes in position 43-46: invalid data

Traceback (most recent call last):
  File "/home/antoranz/instaladores/bzr-1.6b2/bzrlib/commands.py", line 846, in run_bzr_catch_errors
    return run_bzr(argv)
  File "/home/antoranz/instaladores/bzr-1.6b2/bzrlib/commands.py", line 797, in run_bzr
    ret = run(*run_argv)
  File "/home/antoranz/instaladores/bzr-1.6b2/bzrlib/commands.py", line 499, in run_argv_aliases
    return self.run(**all_cmd_args)
  File "/home/antoranz/instaladores/bzr-1.6b2/bzrlib/commands.py", line 807, in ignore_pipe
    result = func(*args, **kwargs)
  File "/home/antoranz/instaladores/bzr-1.6b2/bzrlib/builtins.py", line 178, in run
    show_pending=not no_pending)
  File "/home/antoranz/instaladores/bzr-1.6b2/bzrlib/status.py", line 117, in show_tree_status
    want_unversioned=want_unversioned)
  File "/home/antoranz/instaladores/bzr-1.6b2/bzrlib/tree.py", line 93, in changes_from
    want_unversioned=want_unversioned,
  File "/home/antoranz/instaladores/bzr-1.6b2/bzrlib/decorators.py", line 127, in read_locked
    return unbound(self, *args, **kwargs)
  File "/home/antoranz/instaladores/bzr-1.6b2/bzrlib/tree.py", line 734, in compare
    want_unversioned=want_unversioned)
  File "/home/antoranz/instaladores/bzr-1.6b2/bzrlib/delta.py", line 217, in _compare_trees
    want_unversioned=want_unversioned):
  File "/home/antoranz/instaladores/bzr-1.6b2/bzrlib/workingtree_4.py", line 2450, in iter_changes
    (None, utf8_decode(current_path_info[0])[0]),
  File "/usr/lib/python2.5/encodings/utf_8.py", line 16, in decode
    return codecs.utf_8_decode(input, errors, True)
UnicodeDecodeError: 'utf8' codec can't decode bytes in position 43-46: invalid data

bzr 1.6b2 on python 2.5.2 (linux2)
arguments: ['/home/antoranz/instaladores/bzr-1.6b2/bzr', 'status']
encoding: 'UTF-8', fsenc: 'UTF-8', lang: 'es_CO.UTF-8'
plugins:
  gtk                  /usr/lib/python2.5/site-packages/bzrlib/plugins/gtk [0.93.0]
  launchpad            /home/antoranz/instaladores/bzr-1.6b2/bzrlib/plugins/launchpad [unknown]
*** 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.

The same kind of problem happens with 1.5 (stable):
$ bzr status
bzr: ERROR: exceptions.UnicodeDecodeError: 'utf8' codec can't decode bytes in position 43-46: invalid data

Traceback (most recent call last):
  File "/usr/lib/python2.5/site-packages/bzrlib/commands.py", line 846, in run_bzr_catch_errors
    return run_bzr(argv)
  File "/usr/lib/python2.5/site-packages/bzrlib/commands.py", line 797, in run_bzr
    ret = run(*run_argv)
  File "/usr/lib/python2.5/site-packages/bzrlib/commands.py", line 499, in run_argv_aliases
    return self.run(**all_cmd_args)
  File "/usr/lib/python2.5/site-packages/bzrlib/commands.py", line 807, in ignore_pipe
    result = func(*args, **kwargs)
  File "/usr/lib/python2.5/site-packages/bzrlib/builtins.py", line 178, in run
    show_pending=not no_pending)
  File "/usr/lib/python2.5/site-packages/bzrlib/status.py", line 117, in show_tree_status
    want_unversioned=want_unversioned)
  File "/usr/lib/python2.5/site-packages/bzrlib/tree.py", line 93, in changes_from
    want_unversioned=want_unversioned,
  File "/usr/lib/python2.5/site-packages/bzrlib/decorators.py", line 127, in read_locked
    return unbound(self, *args, **kwargs)
  File "/usr/lib/python2.5/site-packages/bzrlib/tree.py", line 734, in compare
    want_unversioned=want_unversioned)
  File "/usr/lib/python2.5/site-packages/bzrlib/delta.py", line 217, in _compare_trees
    want_unversioned=want_unversioned):
  File "/usr/lib/python2.5/site-packages/bzrlib/workingtree_4.py", line 2432, in iter_changes
    (None, utf8_decode(current_path_info[0])[0]),
  File "/usr/lib/python2.5/encodings/utf_8.py", line 16, in decode
    return codecs.utf_8_decode(input, errors, True)
UnicodeDecodeError: 'utf8' codec can't decode bytes in position 43-46: invalid data

bzr 1.5 on python 2.5.2 (linux2)
arguments: ['/usr/bin/bzr', 'status']
encoding: 'UTF-8', fsenc: 'UTF-8', lang: 'es_CO.UTF-8'
plugins:
  gtk                  /usr/lib/python2.5/site-packages/bzrlib/plugins/gtk [0.93.0]
  launchpad            /usr/lib/python2.5/site-packages/bzrlib/plugins/launchpad [unknown]
*** 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.

Is it my fault and I have to update something?
$ ~/instaladores/bzr-1.6b2/bzr version
Bazaar (bzr) 1.6b2
  Python interpreter: /usr/bin/python 2.5.2
  Python standard library: /usr/lib/python2.5
  bzrlib: /home/antoranz/instaladores/bzr-1.6b2/bzrlib
  Bazaar configuration: /home/antoranz/.bazaar
  Bazaar log file: /home/antoranz/.bzr.log

Copyright 2005, 2006, 2007, 2008 Canonical Ltd.
http://bazaar-vcs.org/

bzr comes with ABSOLUTELY NO WARRANTY.  bzr is free software, and
you may use, modify and redistribute it under the terms of the GNU
General Public License version 2 or later.

$ bzr version
Bazaar (bzr) 1.5
  Python interpreter: /usr/bin/python 2.5.2
  Python standard library: /usr/lib/python2.5
  bzrlib: /usr/lib/python2.5/site-packages/bzrlib
  Bazaar configuration: /home/antoranz/.bazaar
  Bazaar log file: /home/antoranz/.bzr.log

Copyright 2005, 2006, 2007, 2008 Canonical Ltd.
http://bazaar-vcs.org/

bzr comes with ABSOLUTELY NO WARRANTY.  bzr is free software, and
you may use, modify and redistribute it under the terms of the GNU
General Public License version 2 or later.

I'm working on ubuntu hardy and just downloaded bzr1.6b2 and tried to use it.