bzr: ERROR: exceptions.AssertionError: get_next() called when there are no chars left

Try to preview a big merge on Windows XP

bzr: ERROR: exceptions.AssertionError: get_next() called when there are no chars
 left

Traceback (most recent call last):
  File "bzrlib\commands.pyo", line 946, in exception_to_return_code
  File "bzrlib\commands.pyo", line 1150, in run_bzr
  File "bzrlib\commands.pyo", line 699, in run_argv_aliases
  File "bzrlib\commands.pyo", line 721, 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 4016, in run
  File "bzrlib\decorators.pyo", line 154, in read_locked
  File "bzrlib\mutabletree.pyo", line 234, in has_changes
  File "bzrlib\tree.pyo", line 101, in iter_changes
  File "bzrlib\workingtree_4.pyo", line 2181, in iter_changes
  File "bzrlib\dirstate.pyo", line 2425, in _read_dirblocks_if_needed
  File "_dirstate_helpers_pyx.pyx", line 796, in bzrlib._dirstate_helpers_pyx._r
ead_dirblocks (bzrlib\_dirstate_helpers_pyx.c:5500)
  File "_dirstate_helpers_pyx.pyx", line 762, in bzrlib._dirstate_helpers_pyx.Re
ader._parse_dirblocks (bzrlib\_dirstate_helpers_pyx.c:5237)
  File "_dirstate_helpers_pyx.pyx", line 689, in bzrlib._dirstate_helpers_pyx.Re
ader._get_entry (bzrlib\_dirstate_helpers_pyx.c:4779)
  File "_dirstate_helpers_pyx.pyx", line 577, in bzrlib._dirstate_helpers_pyx.Re
ader.get_next_str (bzrlib\_dirstate_helpers_pyx.c:4398)
  File "_dirstate_helpers_pyx.pyx", line 559, in bzrlib._dirstate_helpers_pyx.Re
ader.get_next (bzrlib\_dirstate_helpers_pyx.c:4248)
AssertionError: get_next() called when there are no chars left

bzr 2.4.1 on python 2.6.6 (Windows-XP-5.1.2600-SP3)
arguments: ['bzr', 'merge', '--preview']
plugins: bzrtools[2.4.0], changelog_merge[2.4.1], colo[0.3.1dev],
    explorer[1.2.1], fastimport[0.12.0dev], launchpad[2.4.1], loom[2.2.1dev],
    netrc_credential_store[2.4.1], news_merge[2.4.1], pipeline[1.1.0],
    qbzr[0.21.1], rewrite[0.6.3dev], svn[1.1.0], upload[1.0.1dev],
    xmloutput[0.8.7]
encoding: 'cp1252', fsenc: 'mbcs', lang: None