TypeError on all commands that get progress report from subprocess

In bzr2.5b2 (Installed by bzr2.5b2-1-setup.exe), qcommit does not work.

To reproduce:
  bzr init test
  echo foo>foo
  bzr add
  bzr qcommit -m test
  and clicking OK in the qcommit dialog

Then, it fails with following traceback.

--
Run command: bzr commit -m test foo
bzr: ERROR: exceptions.TypeError: unsupported type u'Collecting changes [0] - Stage'

Traceback (most recent call last):
  File "bzrlib\commands.pyo", line 923, in exception_to_return_code
  File "bzrlib\commands.pyo", line 1128, in run_bzr
  File "bzrlib\commands.pyo", line 676, in run_argv_aliases
  File "bzrlib\commands.pyo", line 698, in run
  File "bzrlib\cleanup.pyo", line 135, in run_simple
  File "bzrlib\cleanup.pyo", line 165, in _do_with_cleanups
  File "C:/Program Files/Bazaar/plugins\qbzr\lib\commands.py", line 821, in run
  File "C:/Program Files/Bazaar/plugins\qbzr\lib\subprocess.py", line 888, in run_subprocess_command
  File "bzrlib\commands.pyo", line 1128, in run_bzr
  File "bzrlib\commands.pyo", line 676, in run_argv_aliases
  File "bzrlib\commands.pyo", line 698, in run
  File "bzrlib\cleanup.pyo", line 135, in run_simple
  File "bzrlib\cleanup.pyo", line 165, in _do_with_cleanups
  File "bzrlib\builtins.pyo", line 3455, in run
  File "bzrlib\decorators.pyo", line 217, in write_locked
  File "bzrlib\workingtree_4.pyo", line 208, in commit
  File "bzrlib\decorators.pyo", line 217, in write_locked
  File "bzrlib\mutabletree.pyo", line 210, in commit
  File "bzrlib\commit.pyo", line 289, in commit
  File "bzrlib\cleanup.pyo", line 131, in run
  File "bzrlib\cleanup.pyo", line 165, in _do_with_cleanups
  File "bzrlib\commit.pyo", line 405, in _commit
  File "bzrlib\commit.pyo", line 959, in _set_progress_stage
  File "bzrlib\commit.pyo", line 972, in _emit_progress
  File "bzrlib\progress.pyo", line 123, in update
  File "bzrlib\ui\text.pyo", line 252, in _progress_updated
  File "bzrlib\ui\text.pyo", line 432, in show_progress
  File "C:/Program Files/Bazaar/plugins\qbzr\lib\subprocess.py", line 804, in _repaint
  File "_bencode_pyx.pyx", line 399, in bzrlib._bencode_pyx.bencode (bzrlib\_bencode_pyx.c:4283)
  File "_bencode_pyx.pyx", line 383, in bzrlib._bencode_pyx.Encoder.process (bzrlib\_bencode_pyx.c:3939)
  File "_bencode_pyx.pyx", line 346, in bzrlib._bencode_pyx.Encoder._encode_list (bzrlib\_bencode_pyx.c:3464)
  File "_bencode_pyx.pyx", line 383, in bzrlib._bencode_pyx.Encoder.process (bzrlib\_bencode_pyx.c:3939)
  File "_bencode_pyx.pyx", line 346, in bzrlib._bencode_pyx.Encoder._encode_list (bzrlib\_bencode_pyx.c:3464)
  File "_bencode_pyx.pyx", line 391, in bzrlib._bencode_pyx.Encoder.process (bzrlib\_bencode_pyx.c:4055)
TypeError: unsupported type u'Collecting changes [0] - Stage'

bzr 2.5b2 on python 2.6.6 (Windows-7-6.1.7600)
arguments: ['C:\\Program Files\\Bazaar\\bzr.exe', 'qsubprocess', '--bencode',
    'l6:commit2:-m4:test3:fooe']
plugins: bzrtools[2.4.1], colo[0.3.1dev], explorer[1.2.1], launchpad[2.5b2],
    loom[2.2.1dev], pipeline[1.1.0], qbzr[0.21.1], rewrite[0.6.3dev],
    svn[1.1.0], xmloutput[0.8.7]
encoding: 'cp932', fsenc: 'mbcs', lang: 'ja'

*** Bazaar has encountered an internal error. This probably indicates a
    bug in Bazaar. You can help us fix it by filing a bug report at
        https://bugs.launchpad.net/bzr/+filebug
    including this traceback and a description of the problem.