I believe I'm having the same problem with one of my branches. I'm includig the bzr check as requested by Robert Collins.

$ bzr upload
Using saved location: sftp://<email address hidden>/home/josiah/public_html/sites/ptsic.domain.com/
bzr: ERROR: bzrlib.errors.NoSuchRevision: KnitPackRepository('file:///Users/Josiah/htdocs/drupal-6.10/sites/ptsic.localhost/.bzr/repository/') has no revision ('<email address hidden>',)

Traceback (most recent call last):
  File "/Library/Python/2.5/site-packages/bzrlib/commands.py", line 896, in run_bzr_catch_errors
    return run_bzr(argv)
  File "/Library/Python/2.5/site-packages/bzrlib/commands.py", line 842, in run_bzr
    ret = run(*run_argv)
  File "/Library/Python/2.5/site-packages/bzrlib/commands.py", line 542, in run_argv_aliases
    return self.run(**all_cmd_args)
  File "/Users/Josiah/.bazaar/plugins/upload/__init__.py", line 420, in run
    uploader.upload_tree()
  File "/Users/Josiah/.bazaar/plugins/upload/__init__.py", line 267, in upload_tree
    from_tree = self.branch.repository.revision_tree(rev_id)
  File "/Library/Python/2.5/site-packages/bzrlib/decorators.py", line 138, in read_locked
    result = unbound(self, *args, **kwargs)
  File "/Library/Python/2.5/site-packages/bzrlib/repository.py", line 1809, in revision_tree
    inv = self.get_revision_inventory(revision_id)
  File "/Library/Python/2.5/site-packages/bzrlib/decorators.py", line 138, in read_locked
    result = unbound(self, *args, **kwargs)
  File "/Library/Python/2.5/site-packages/bzrlib/repository.py", line 1772, in get_revision_inventory
    return self.get_inventory(revision_id)
  File "/Library/Python/2.5/site-packages/bzrlib/decorators.py", line 138, in read_locked
    result = unbound(self, *args, **kwargs)
  File "/Library/Python/2.5/site-packages/bzrlib/repository.py", line 1663, in get_inventory
    return self.iter_inventories([revision_id]).next()
  File "/Library/Python/2.5/site-packages/bzrlib/repository.py", line 1681, in _iter_inventories
    for text, revision_id in self._iter_inventory_xmls(revision_ids):
  File "/Library/Python/2.5/site-packages/bzrlib/repository.py", line 1692, in _iter_inventory_xmls
    raise errors.NoSuchRevision(self, record.key)
NoSuchRevision: KnitPackRepository('file:///Users/Josiah/htdocs/drupal-6.10/sites/ptsic.localhost/.bzr/repository/') has no revision ('<email address hidden>',)

bzr 1.12 on python 2.5.1 (darwin)
arguments: ['/usr/local/bin/bzr', 'upload']
encoding: 'UTF-8', fsenc: 'utf-8', lang: 'en_US.UTF-8'
plugins:
  automv               /Users/Josiah/.bazaar/plugins/automv [unknown]
  bzr_push_and_update  /Users/Josiah/.bazaar/plugins/bzr_push_and_update [0.2dev]
  bzrtools             /Library/Python/2.5/site-packages/bzrlib/plugins/bzrtools [1.12]
  difftools            /Users/Josiah/.bazaar/plugins/difftools [0.91]
  email                /Library/Python/2.5/site-packages/bzrlib/plugins/email [unknown]
  extmerge             /Library/Python/2.5/site-packages/bzrlib/plugins/extmerge [unknown]
  launchpad            /Library/Python/2.5/site-packages/bzrlib/plugins/launchpad [unknown]
  loom                 /Library/Python/2.5/site-packages/bzrlib/plugins/loom [1.4dev]
  netrc_credential_store /Library/Python/2.5/site-packages/bzrlib/plugins/netrc_credential_store [unknown]
  qbzr                 /Library/Python/2.5/site-packages/bzrlib/plugins/qbzr [0.9.8]
  rebase               /Library/Python/2.5/site-packages/bzrlib/plugins/rebase [0.4dev]
  search               /Library/Python/2.5/site-packages/bzrlib/plugins/search [1.7dev]
  svn                  /Library/Python/2.5/site-packages/bzrlib/plugins/svn [0.5.2]
  upload               /Users/Josiah/.bazaar/plugins/upload [1.0dev]
*** Bazaar has encountered an internal error.
    Please report a bug at https://bugs.launchpad.net/bzr/+filebug
    including this traceback, and a description of what you
    were doing when the error occurred.
Macintosh-16:ptsic Josiah$ bzr check
Checking working tree at 'file:///Users/Josiah/htdocs/drupal-6.10/sites/ptsic.localhost/'.
Checking repository at 'file:///Users/Josiah/htdocs/drupal-6.10/sites/ptsic.localhost/'.
checked repository <bzrlib.transport.local.LocalTransport url=file:///Users/Josiah/htdocs/drupal-6.10/sites/ptsic.localhost/> format <RepositoryFormatKnitPack1>
    22 revisions
   231 file-ids
   226 unique file texts
   953 repeated file texts
     0 unreferenced text versions
Checking branch at 'file:///Users/Josiah/htdocs/drupal-6.10/sites/ptsic.localhost/'.
checked branch file:///Users/Josiah/htdocs/drupal-6.10/sites/ptsic.localhost/ format Bazaar Branch Format 6 (bzr 0.15)
Macintosh-16:ptsic Josiah$ bzr update
Tree is up to date at revision 22.