'bzr: ERROR: Not a branch' on existing local branch. Can I repair it?

[Stevens, Ian]

> Can you give the output from "My Documents\.bzr.log" after running a
> command?

bzr arguments: [u'diff']
looking for plugins in c:\Program
Files\Bazaar\lib\library.zip\bzrlib\plugins
looking for plugins in C:/Documents and Settings/istevens/Application
Data/bazaar/2.0/plugins
Looking for plugins in 'c:\\Program
Files\\Bazaar\\lib\\library.zip\\bzrlib\\plugins'
Names in archive: ['__init__.pyc', 'launchpad/__init__.pyc',
'launchpad/lp_registration.pyc', 'launc
hpad/test_register.pyc']
Load plugin launchpad from zip 'c:\\Program
Files\\Bazaar\\lib\\library.zip\\bzrlib\\plugins'
Traceback (most recent call last):
  File "bzrlib\commands.pyc", line 650, in run_bzr_catch_errors
  File "bzrlib\commands.pyc", line 612, in run_bzr
  File "bzrlib\commands.pyc", line 304, in run_argv_aliases
  File "bzrlib\commands.pyc", line 622, in ignore_pipe
  File "bzrlib\builtins.pyc", line 1235, in run
  File "bzrlib\builtins.pyc", line 85, in internal_tree_files
  File "bzrlib\workingtree.pyc", line 348, in open_containing
  File "bzrlib\bzrdir.pyc", line 530, in open_containing
  File "bzrlib\bzrdir.pyc", line 558, in open_containing_from_transport
NotBranchError: Not a branch: C:/Documents and
Settings/istevens/dev/ticker/trunk/
return code 3

> Have you used a newer bzr at all (0.15?).

No, only 0.14.0.
 
> Also, can you tell us what files exist in .bzr\branch ?

Both branches which give the error contain only the lock/ dir and a
revision-history file.  The ones which work contain those files as well
as branch-name, format and parent files.

Ian.