Comment 6 for bug 389413

And when doing a checkout of a 1.6 branch:

/usr/bin/bzr checkout --revision 851 bzr+ssh://server/trunk build

bzr: ERROR: bzrlib.errors.ObjectNotLocked: _KnitGraphIndex(CombinedGraphIndex()) is not locked

Traceback (most recent call last):
  File "/usr/lib/python2.5/site-packages/bzrlib/commands.py", line 835, in exception_to_return_code
    return the_callable(*args, **kwargs)
  File "/usr/lib/python2.5/site-packages/bzrlib/commands.py", line 1030, in run_bzr
    ret = run(*run_argv)
  File "/usr/lib/python2.5/site-packages/bzrlib/commands.py", line 647, in run_argv_aliases
    return self.run(**all_cmd_args)
  File "/usr/lib/python2.5/site-packages/bzrlib/builtins.py", line 1316, in run
    revision_id = revision.as_revision_id(source)
  File "/usr/lib/python2.5/site-packages/bzrlib/revisionspec.py", line 243, in as_revision_id
    return self._as_revision_id(context_branch)
  File "/usr/lib/python2.5/site-packages/bzrlib/revisionspec.py", line 387, in _as_revision_id
    branch, revno, revision_id = self._lookup(context_branch, None)
  File "/usr/lib/python2.5/site-packages/bzrlib/revisionspec.py", line 380, in _lookup
    revision_id = branch.get_rev_id(revno, revs_or_none)
  File "/usr/lib/python2.5/site-packages/bzrlib/remote.py", line 2271, in get_rev_id
    revno, last_revision_info)
  File "/usr/lib/python2.5/site-packages/bzrlib/remote.py", line 696, in get_rev_id_for_revno
    return self._get_rev_id_for_revno_vfs(revno, known_pair)
  File "/usr/lib/python2.5/site-packages/bzrlib/remote.py", line 684, in _get_rev_id_for_revno_vfs
    revno, known_pair)
  File "/usr/lib/python2.5/site-packages/bzrlib/repository.py", line 2269, in get_rev_id_for_revno
    self, partial_history, stop_index=distance_from_known)
  File "/usr/lib/python2.5/site-packages/bzrlib/repository.py", line 4370, in _iter_for_revno
    iterator.next()
  File "/usr/lib/python2.5/site-packages/bzrlib/repository.py", line 2299, in iter_reverse_revision_history
    parents = graph.get_parent_map([next_id])[next_id]
  File "/usr/lib/python2.5/site-packages/bzrlib/graph.py", line 167, in get_parent_map
    parent_map = self._get_parent_map(needed_revisions)
  File "/usr/lib/python2.5/site-packages/bzrlib/repository.py", line 2457, in get_parent_map
    self.revisions.get_parent_map(query_keys).iteritems():
  File "/usr/lib/python2.5/site-packages/bzrlib/knit.py", line 1193, in get_parent_map
    return self._get_parent_map_with_sources(keys)[0]
  File "/usr/lib/python2.5/site-packages/bzrlib/knit.py", line 1212, in _get_parent_map_with_sources
    new_result = source.get_parent_map(missing)
  File "/usr/lib/python2.5/site-packages/bzrlib/knit.py", line 3047, in get_parent_map
    self._check_read()
  File "/usr/lib/python2.5/site-packages/bzrlib/knit.py", line 2930, in _check_read
    raise errors.ObjectNotLocked(self)
ObjectNotLocked: _KnitGraphIndex(CombinedGraphIndex()) is not locked

bzr 1.17 on python 2.5.2 (linux2)
arguments: ['/usr/bin/bzr', 'checkout', '--revision', '851', 'bzr+ssh://server/trunk', 'build']
encoding: 'UTF-8', fsenc: 'UTF-8', lang: 'en_US.UTF-8'
plugins:
  bzrtools /usr/lib/python2.5/site-packages/bzrlib/plugins/bzrtools [1.17]
  launchpad /usr/lib/python2.5/site-packages/bzrlib/plugins/launchpad [1.17]
  mirror /var/lib/buildbot/.bazaar/plugins/mirror [unknown]
  netrc_credential_store /usr/lib/python2.5/site-packages/bzrlib/plugins/netrc_credential_store [1.17]
  qbzr /usr/lib/python2.5/site-packages/bzrlib/plugins/qbzr [0.13.1]
*** 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.

After downgrading to bzr-1.16.1-1~bazaar1~intrepid, it works.