ObjectNotLocked opening diff from annotate on 2a branch.

bzr: ERROR: bzrlib.errors.ObjectNotLocked: <bzrlib.groupcompress._GCGraphIndex object at 0x015EABF0> is not locked

Traceback (most recent call last):
  File "D:\My Documents\bzr-plugins\qbzr\lib\trace.py", line 286, in reports_exception_decorate
  File "D:\My Documents\bzr-plugins\qbzr\lib\diffwindow.py", line 205, in initial_load
  File "D:\My Documents\bzr-plugins\qbzr\lib\diffwindow.py", line 214, in load_branch_info
  File "D:\My Documents\bzr-plugins\qbzr\lib\diff_arg.py", line 82, in get_diff_window_args
  File "D:\My Documents\bzr-plugins\qbzr\lib\diff_arg.py", line 77, in load_new_tree_and_paths
  File "bzrlib\tree.pyo", line 160, in id2path
  File "bzrlib\inventory.pyo", line 758, in id2path
  File "bzrlib\inventory.pyo", line 1826, in _iter_file_id_parents
  File "bzrlib\inventory.pyo", line 1808, in __getitem__
  File "bzrlib\chk_map.pyo", line 470, in iteritems
  File "bzrlib\chk_map.pyo", line 124, in _ensure_root
  File "bzrlib\chk_map.pyo", line 137, in _get_node
  File "bzrlib\chk_map.pyo", line 148, in _read_bytes
  File "bzrlib\groupcompress.pyo", line 1190, in get_record_stream
  File "bzrlib\groupcompress.pyo", line 1295, in _get_remaining_record_stream
  File "bzrlib\groupcompress.pyo", line 1764, in get_build_details
  File "bzrlib\groupcompress.pyo", line 1688, in _check_read
ObjectNotLocked: <bzrlib.groupcompress._GCGraphIndex object at 0x015EABF0> is not locked

bzr 1.17 on python 2.5.4 (win32)
arguments: ['bzr', 'qannotate', 'main.asp']
encoding: 'cp1252', fsenc: 'mbcs', lang: None
plugins:
  bzrtools C:\Program Files\Bazaar\plugins\bzrtools [1.17]
  difftools D:\My Documents\bzr-plugins\difftools [0.91]
  extmerge D:\My Documents\bzr-plugins\extmerge [unknown]
  launchpad C:\Program Files\Bazaar\plugins\launchpad [1.17]
  netrc_credential_store C:\Program Files\Bazaar\plugins\netrc_credential_store [1.17]
  qbzr D:\My Documents\bzr-plugins\qbzr [0.15dev]
  rebase C:\Program Files\Bazaar\plugins\rebase [0.5.2]
  search D:\My Documents\bzr-plugins\search [1.6.0.dev.3]
  svn C:\Program Files\Bazaar\plugins\svn [0.6.3]
  upload D:\My Documents\bzr-plugins\upload [0.1.1]