I am seeing this issue too.  I do not use gannotate or viz or any GTK.  I am just checking out a straight, exclusive Python branch.  I have seen this once before and found no way to cure it!  It is extremely vexing because once this occurs, it is permanent and a whole new fresh checkout of the 1/3 gb of data in the Python repository must be downloaded fresh and one must start again!  This takes an EXTREMELY long time.  And this seems to effect every bzr operation from switching to merging.

Here is my error report:

bzr: ERROR: bzrlib.errors.LockContention: Could not acquire lock "[Errno 11] Resource temporarily unavailable"

Traceback (most recent call last):
  File "/home/crew/user/lib/python2.5/site-packages/bzrlib/commands.py", line 846, in run_bzr_catch_errors
    return run_bzr(argv)
  File "/home/crew/user/lib/python2.5/site-packages/bzrlib/commands.py", line 797, in run_bzr
    ret = run(*run_argv)
  File "/home/crew/user/lib/python2.5/site-packages/bzrlib/commands.py", line 499, in run_argv_aliases
    return self.run(**all_cmd_args)
  File "/home/crew/user/lib/python2.5/site-packages/bzrlib/builtins.py", line 4497, in run
    switch.switch(control_dir, to_branch, force)
  File "/home/crew/user/lib/python2.5/site-packages/bzrlib/switch.py", line 39, in switch
    _update(tree, source_repository)
  File "/home/crew/user/lib/python2.5/site-packages/bzrlib/switch.py", line 121, in _update
    tree.lock_tree_write()
  File "/home/crew/user/lib/python2.5/site-packages/bzrlib/workingtree_4.py", line 621, in lock_tree_write
    self._lock_self_write()
  File "/home/crew/user/lib/python2.5/site-packages/bzrlib/workingtree_4.py", line 605, in _lock_self_write
    state.lock_write()
  File "/home/crew/user/lib/python2.5/site-packages/bzrlib/dirstate.py", line 2734, in lock_write
    self._lock_token = lock.WriteLock(self._filename)
  File "/home/crew/user/lib/python2.5/site-packages/bzrlib/lock.py", line 146, in __init__
    raise errors.LockContention(e)
LockContention: Could not acquire lock "[Errno 11] Resource temporarily unavailable"

bzr 1.5 on python 2.5.2 (linux2)
arguments: ['/home/crew/user/bin/bzr', 'swre9+10', '-Derror']
encoding: 'ANSI_X3.4-1968', fsenc: 'ANSI_X3.4-1968', lang: None
plugins:
  bzrtools             /home/crew/user/lib/python2.5/site-packages/bzrlib/plugins/bzrtools [1.5.0]
  checkeol             /home/crew/user/lib/python2.5/site-packages/bzrlib/plugins/checkeol [1.2.1]
  diffstat             /home/crew/user/lib/python2.5/site-packages/bzrlib/plugins/diffstat [unknown]
  launchpad            /home/crew/user/lib/python2.5/site-packages/bzrlib/plugins/launchpad [unknown]
  lessdiff             /home/crew/user/lib/python2.5/site-packages/bzrlib/plugins/lessdiff [unknown]
  lesslog              /home/crew/user/lib/python2.5/site-packages/bzrlib/plugins/lesslog [unknown]
  rebase               /home/crew/user/lib/python2.5/site-packages/bzrlib/plugins/rebase [0.3.0]
  stats                /home/crew/user/lib/python2.5/site-packages/bzrlib/plugins/stats [unknown]
*** 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.

-----

And when I try to break locks:

bzr: ERROR: bzrlib.errors.LockActive: The lock for '/home/crew/user/Regexp-2.6' is in use and cannot be broken.

Traceback (most recent call last):
  File "/home/crew/user/lib/python2.5/site-packages/bzrlib/commands.py", line 846, in run_bzr_catch_errors
    return run_bzr(argv)
  File "/home/crew/user/lib/python2.5/site-packages/bzrlib/commands.py", line 797, in run_bzr
    ret = run(*run_argv)
  File "/home/crew/user/lib/python2.5/site-packages/bzrlib/commands.py", line 499, in run_argv_aliases
    return self.run(**all_cmd_args)
  File "/home/crew/user/lib/python2.5/site-packages/bzrlib/builtins.py", line 3770, in run
    control.break_lock()
  File "/home/crew/user/lib/python2.5/site-packages/bzrlib/bzrdir.py", line 117, in break_lock
    thing_to_unlock.break_lock()
  File "/home/crew/user/lib/python2.5/site-packages/bzrlib/workingtree_4.py", line 216, in break_lock
    raise errors.LockActive(self.basedir)
LockActive: The lock for '/home/crew/user/Regexp-2.6' is in use and cannot be broken.

bzr 1.5 on python 2.5.2 (linux2)
arguments: ['/home/crew/user/bin/bzr', 'break-lock', '-Derror']
encoding: 'ANSI_X3.4-1968', fsenc: 'ANSI_X3.4-1968', lang: None
plugins:
  bzrtools             /home/crew/user/lib/python2.5/site-packages/bzrlib/plugins/bzrtools [1.5.0]
  checkeol             /home/crew/user/lib/python2.5/site-packages/bzrlib/plugins/checkeol [1.2.1]
  diffstat             /home/crew/user/lib/python2.5/site-packages/bzrlib/plugins/diffstat [unknown]
  launchpad            /home/crew/user/lib/python2.5/site-packages/bzrlib/plugins/launchpad [unknown]
  lessdiff             /home/crew/user/lib/python2.5/site-packages/bzrlib/plugins/lessdiff [unknown]
  lesslog              /home/crew/user/lib/python2.5/site-packages/bzrlib/plugins/lesslog [unknown]
  rebase               /home/crew/user/lib/python2.5/site-packages/bzrlib/plugins/rebase [0.3.0]
  stats                /home/crew/user/lib/python2.5/site-packages/bzrlib/plugins/stats [unknown]
*** 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.


-----

Please help.