Comment 9 for bug 369038

I don't know if this can help but i've got the same problem, i mean nothing happen when i laucnh "ubuntuOne" from the menu (no web pages, no launcher on the top panel bar).
I killed 2 processes and relaunch ubuntuone-client-applet --signup
Here is the result :

/usr/lib/python2.6/dist-packages/canonical/ubuntuone/oauthdesktop/auth.py:191: DeprecationWarning: BaseException.message has been deprecated as of Python 2.6
  raise UnknownLoginError(e.message)
Traceback (most recent call last):
  File "/var/lib/python-support/python2.6/dbus/connection.py", line 578, in msg_reply_handler
    reply_handler(*message.get_args_list(**get_args_opts))
  File "/usr/lib/python2.6/dist-packages/canonical/ubuntuone/oauthdesktop/auth.py", line 230, in got_state
    self.acquire_access_token(description, store)
  File "/usr/lib/python2.6/dist-packages/canonical/ubuntuone/oauthdesktop/auth.py", line 283, in acquire_access_token
    self.request_token = self.make_token_request(oauth_request)
  File "/usr/lib/python2.6/dist-packages/canonical/ubuntuone/oauthdesktop/auth.py", line 191, in make_token_request
    raise UnknownLoginError(e.message)
canonical.ubuntuone.oauthdesktop.auth.UnknownLoginError

... and it "freeze" and don't give me the prompt back (i've got to do a ctrl+C)

My spec :
Ubuntu 9.04 uptodate
Gnome
Firefox 3.0.11
Intel32
Linux cogito 2.6.28-13-generic #45-Ubuntu SMP Tue Jun 30 19:49:51 UTC 2009 i686 GNU/Linux