not able to branch from launchpad behind proxy (squid)

Hello,
what settings do I need to configure in Squid firewall to let bazaar branch from Launchpad?

For SVN we needed to add:
 extension_methods REPORT MERGE MKACTIVITY CHECKOUT PROPFIND

The proxy doesn't let bazaar access external servers:

D:\>bzr branch lp:bzr
No module named mercurial.commands
Unable to load plugin u'hg' from u'C:/Programme/Bazaar/plugins'
bzr-git: Please install dulwich, https://launchpad.net/dulwich
Unable to load plugin u'dulwich' from u'C:/Programme/Bazaar/plugins'
bzr: ERROR: socket.error: (10060, 'Operation timed out')

Traceback (most recent call last):
  File "bzrlib\commands.pyo", line 893, in run_bzr_catch_errors
  File "bzrlib\commands.pyo", line 839, in run_bzr
  File "bzrlib\commands.pyo", line 539, in run_argv_aliases
  File "bzrlib\builtins.pyo", line 1010, in run
  File "bzrlib\bzrdir.pyo", line 891, in open_tree_or_branch
  File "bzrlib\bzrdir.pyo", line 777, in open
  File "bzrlib\lazy_import.pyo", line 125, in __call__
  File "bzrlib\transport\__init__.pyo", line 1574, in get_transport
  File "bzrlib\directory_service.pyo", line 58, in dereference
  File "C:/Programme/Bazaar/plugins\launchpad\lp_directory.py", line 60, in look_up
  File "C:/Programme/Bazaar/plugins\launchpad\lp_directory.py", line 76, in _resolve
  File "C:/Programme/Bazaar/plugins\launchpad\lp_registration.py", line 182, in submit
  File "C:/Programme/Bazaar/plugins\launchpad\lp_registration.py", line 147, in send_request
  File "xmlrpclib.pyo", line 1147, in __call__
  File "xmlrpclib.pyo", line 1437, in __request
  File "xmlrpclib.pyo", line 1183, in request
  File "xmlrpclib.pyo", line 1297, in send_content
  File "httplib.pyo", line 860, in endheaders
  File "httplib.pyo", line 732, in _send_output
  File "httplib.pyo", line 699, in send
  File "httplib.pyo", line 1134, in connect
  File "<string>", line 1, in connect
error: (10060, 'Operation timed out')

bzr 1.11 on python 2.5.2 (win32)
arguments: ['bzr', 'branch', 'lp:bzr']
encoding: 'cp1252', fsenc: 'mbcs', lang: 'de'
plugins:
  bzrtools C:\Programme\Bazaar\plugins\bzrtools [1.11]
  difftools C:\Programme\Bazaar\plugins\difftools [0.91]
  extmerge C:\Programme\Bazaar\plugins\extmerge [unknown]
  launchpad C:\Programme\Bazaar\plugins\launchpad [unknown]
  netrc_credential_store C:\Programme\Bazaar\plugins\netrc_credential_store [unknown]
  push_and_update C:\Programme\Bazaar\plugins\push_and_update [0.2dev]
  qbzr C:\Programme\Bazaar\plugins\qbzr [0.9.6]
  svn C:\Programme\Bazaar\plugins\svn [0.4.17]
  upload C:\Programme\Bazaar\plugins\upload [1.0dev]
  xmloutput C:\Programme\Bazaar\plugins\xmloutput [0.8.1]
*** 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.

Help is highly appreciated.
Thanks!