Somehow I could solve the above, original situation.

But I've just ran into something similar again and wanted to note that reverting does not appear to help, but fails with an error on its own:

bzr: ERROR: bzrlib.errors.PathNotChild: Path "/home/daniel/dev/simpletest/docs" is not a child of path "/home/daniel/src/b2evo/dev.local"

Traceback (most recent call last):
  File "/usr/lib/python2.5/site-packages/bzrlib/commands.py", line 846, in run_bzr_catch_errors
    return run_bzr(argv)
  File "/usr/lib/python2.5/site-packages/bzrlib/commands.py", line 797, in run_bzr
    ret = run(*run_argv)
  File "/usr/lib/python2.5/site-packages/bzrlib/commands.py", line 499, in run_argv_aliases
    return self.run(**all_cmd_args)
  File "/usr/lib/python2.5/site-packages/bzrlib/builtins.py", line 3201, in run
    self._revert_tree_to_revision(tree, revision, file_list, no_backup)
  File "/usr/lib/python2.5/site-packages/bzrlib/builtins.py", line 3215, in _revert_tree_to_revision
    not no_backup, pb, report_changes=True)
  File "/usr/lib/python2.5/site-packages/bzrlib/mutabletree.py", line 52, in tree_write_locked
    return unbound(self, *args, **kwargs)
  File "/usr/lib/python2.5/site-packages/bzrlib/workingtree.py", line 1943, in revert
    report_changes)
  File "/usr/lib/python2.5/site-packages/bzrlib/transform.py", line 1895, in revert
    lambda t, c: conflict_pass(t, c, target_tree))
  File "/usr/lib/python2.5/site-packages/bzrlib/transform.py", line 2016, in resolve_conflicts
    conflicts = tt.find_conflicts()
  File "/usr/lib/python2.5/site-packages/bzrlib/transform.py", line 580, in find_conflicts
    self._add_tree_children()
  File "/usr/lib/python2.5/site-packages/bzrlib/transform.py", line 611, in _add_tree_children
    list(self.iter_tree_children(parent_id))
  File "/usr/lib/python2.5/site-packages/bzrlib/transform.py", line 630, in iter_tree_children
    yield self.trans_id_tree_path(childpath)
  File "/usr/lib/python2.5/site-packages/bzrlib/transform.py", line 293, in trans_id_tree_path
    path = self.canonical_path(path)
  File "/usr/lib/python2.5/site-packages/bzrlib/transform.py", line 287, in canonical_path
    relpath = self._tree.relpath(abs)
  File "/usr/lib/python2.5/site-packages/bzrlib/workingtree.py", line 416, in relpath
    return osutils.relpath(self.basedir, path)
  File "/usr/lib/python2.5/site-packages/bzrlib/osutils.py", line 884, in relpath
    raise errors.PathNotChild(rp, base)
PathNotChild: Path "/home/daniel/dev/simpletest/docs" is not a child of path "/home/daniel/src/b2evo/dev.local"

bzr 1.5 on python 2.5.2 (linux2)
arguments: ['/usr/bin/bzr', 'revert', '.']
encoding: 'UTF-8', fsenc: 'UTF-8', lang: 'de_DE.UTF-8'
plugins:
  builddeb             /usr/lib/python2.5/site-packages/bzrlib/plugins/builddeb [0.92.0dev0]
  bzrtools             /usr/lib/python2.5/site-packages/bzrlib/plugins/bzrtools [1.5.0]
  gtk                  /usr/lib/python2.5/site-packages/bzrlib/plugins/gtk [0.94.0]
  launchpad            /usr/lib/python2.5/site-packages/bzrlib/plugins/launchpad [unknown]
  qbzr                 /usr/lib/python2.5/site-packages/bzrlib/plugins/qbzr [0.9.0]
  rebase               /usr/lib/python2.5/site-packages/bzrlib/plugins/rebase [0.3.0]