Stack trace on colo branch merge/update

Following the standard process for using colo (as I understand it, apologies if I have it wrong) I cannot merge from a branch back into the trunk. When I try to commit I can't however it says to run "update" but doing so results in a stack trace. Here are the rough steps I perform but I have included console output later on in the report.

Steps:
  - Create colo workspace
  - colo-init
  - Create a branch (and switch to it)
  - Do stuff.
  - Commit changes
  - switch to trunk
  - merge changes
  - bzr status - says to update
  - bzr update - CRASH
  - bzr commit - won't commit.

Please accept my apologies if this is just user error but thought I would raise the bug in case it wasn't.

Alex

Details
---------
OS: Ubuntu 10.10
Bazaar - 2.2.3 (from PPA)
Plugins:
  - bash_completion 2.2.3
  - bzrtools 2.2.0
  - colo 0.2.0
  - launchpad 2.2.3
  - netrc_credential_store 2.2.3
  - news_merge 2.2.3
  - pipeline 1.1.0
  - svn 1.0.4

Commands and Output
-----------------------------
(09:20:00) projects> mkdir colo_test
(09:20:11) projects> cd colo_test/
(09:20:16) colo_test> bzr colo-init
(09:20:25) colo_test> bzr colo-branch branch1
Branched 0 revision(s).
Tree is up to date at revision 0.
Switched to branch: /media/Main/dev/projects/colo_test/.bzr/branches/branch1/
(09:20:38) colo_test> touch newfile.txt
(09:20:49) colo_test> gvim newfile.txt
(09:20:53) colo_test> bzr add newfile.txt
.bzr/ newfile.txt
(09:20:53) colo_test> bzr add newfile.txt
adding newfile.txt
(09:21:10) colo_test> bzr commit -m "Added new file"
Committing to: /media/Main/dev/projects/colo_test/.bzr/branches/branch1/
added newfile.txt
Committed revision 1.
(09:21:18) colo_test> bzr switch colo:trunk
Updated to revision 0.
Switched to branch: /media/Main/dev/projects/colo_test/.bzr/branches/trunk/
(09:21:29) colo_test> bzr status
(09:21:32) colo_test> bzr merge colo:branch1
+N newfile.txt
All changes applied successfully.
(09:21:40) colo_test> bzr status
working tree is out of date, run 'bzr update'
(09:21:43) colo_test> bzr update
bzr: failed to report crash using apport:
     OSError(13, 'Permission denied')
bzr: ERROR: exceptions.ValueError: WorkingTree.set_root_id with fileid=None

Traceback (most recent call last):
  File "/usr/lib/python2.6/dist-packages/bzrlib/commands.py", line 912, in exception_to_return_code
    return the_callable(*args, **kwargs)
  File "/usr/lib/python2.6/dist-packages/bzrlib/commands.py", line 1112, in run_bzr
    ret = run(*run_argv)
  File "/usr/lib/python2.6/dist-packages/bzrlib/commands.py", line 690, in run_argv_aliases
    return self.run(**all_cmd_args)
  File "/usr/lib/python2.6/dist-packages/bzrlib/commands.py", line 705, in run
    return self._operation.run_simple(*args, **kwargs)
  File "/usr/lib/python2.6/dist-packages/bzrlib/cleanup.py", line 135, in run_simple
    self.cleanups, self.func, *args, **kwargs)
  File "/usr/lib/python2.6/dist-packages/bzrlib/cleanup.py", line 165, in _do_with_cleanups
    result = func(*args, **kwargs)
  File "/usr/lib/python2.6/dist-packages/bzrlib/builtins.py", line 1440, in run
    old_tip=old_tip)
  File "/usr/lib/python2.6/dist-packages/bzrlib/workingtree.py", line 2262, in update
    return self._update_tree(old_tip, change_reporter, revision)
  File "/usr/lib/python2.6/dist-packages/bzrlib/mutabletree.py", line 50, in tree_write_locked
    return unbound(self, *args, **kwargs)
  File "/usr/lib/python2.6/dist-packages/bzrlib/workingtree.py", line 2317, in _update_tree
    self.set_root_id(to_root_id)
  File "/usr/lib/python2.6/dist-packages/bzrlib/mutabletree.py", line 50, in tree_write_locked
    return unbound(self, *args, **kwargs)
  File "/usr/lib/python2.6/dist-packages/bzrlib/workingtree.py", line 2175, in set_root_id
    'WorkingTree.set_root_id with fileid=None')
ValueError: WorkingTree.set_root_id with fileid=None

bzr 2.2.3 on python 2.6.6 (Linux-2.6.35-24-generic-i686-with-Ubuntu-10.10-maverick)
arguments: ['/usr/bin/bzr', 'update']
encoding: 'UTF-8', fsenc: 'UTF-8', lang: 'en_GB.utf8'
plugins:
  bash_completion /usr/lib/python2.6/dist-packages/bzrlib/plugins/bash_completion [2.2.3]
  bzrtools /usr/lib/python2.6/dist-packages/bzrlib/plugins/bzrtools [2.2.0]
  colo /home/alewis/.bazaar/plugins/colo [0.2.0]
  launchpad /usr/lib/python2.6/dist-packages/bzrlib/plugins/launchpad [2.2.3]
  netrc_credential_store /usr/lib/python2.6/dist-packages/bzrlib/plugins/netrc_credential_store [2.2.3]
  news_merge /usr/lib/python2.6/dist-packages/bzrlib/plugins/news_merge [2.2.3]
  pipeline /usr/lib/python2.6/dist-packages/bzrlib/plugins/pipeline [1.1.0]
  svn /usr/lib/python2.6/dist-packages/bzrlib/plugins/svn [1.0.4]

*** Bazaar has encountered an internal error. This probably indicates a
    bug in Bazaar. You can help us fix it by filing a bug report at
        https://bugs.launchpad.net/bzr/+filebug
    including this traceback and a description of the problem.
(09:21:48) colo_test> bzr commit -m "Trying to commit"
Committing to: /media/Main/dev/projects/colo_test/.bzr/branches/trunk/
aborting commit write group: PointlessCommit(No changes to commit)
bzr: ERROR: No changes to commit. Use --unchanged to commit anyhow.
(09:29:20) colo_test>