failure to display changeset in "qlog" when entered from "qbrowse"

Steps to reproduce

1. "bzr qbrowse"
2. select a file -> "show log..." -> log window opens
3. select a revision ->
     a) revision file list (in the bottom right corner) doesn't get displayed
     b) traceback in the cosole

---

Traceback (most recent call last):
  File "C:/Documents and Settings/xkm/Application Data/bazaar/2.0/plugins\qbzr\log.py", line 364, in update_selection
    [rev]).next()
  File "bzrlib\repository.pyc", line 1087, in get_deltas_for_revisions
  File "bzrlib\repository.pyc", line 1086, in <genexpr>
  File "bzrlib\repository.pyc", line 1631, in revision_trees
  File "bzrlib\repofmt\pack_repo.pyc", line 1948, in get_inventory_weave
  File "bzrlib\repofmt\pack_repo.pyc", line 1804, in get_weave
  File "bzrlib\repofmt\pack_repo.pyc", line 1330, in ensure_loaded
bzrlib.errors.ObjectNotLocked: KnitPackRepository(u'file:///D:/xkm/projects/.bzr/repository/') is not locked