ldtp fails with alacarte with error xmlrpclib.Fault: <Fault 8002: "'NoneType' object has no attribute '_narrow'">

Binary package hint: ldtp

ldtp fails to work with alacarte. I see the main window in the window list but get an error as soon as I try to do something with it.
Accerciser works correctly and can navigate the components tree

TEST CASE:
$ python
>>> import ldtp
>>> ldtp.launchapp('alacarte')
>>> ldtp.getwindowlist()
['frmDesktop', 'frmTopExpandedEdgePanel', 'frmBottomExpandedEdgePanel', 'dlg0', 'dlg1', 'frmj-lallement@black:~/.xchat2/xchatlogs', 'frmCanonical:#qa', 'frmLaunchpad-Canonical-MozillaThunderbird', 'frmWrite:StatusReport2011W04', u'frmReportabugabout\u201cldtp\u201dpackageinUbuntu:Bugs:\u201cldtp\u201dpackage:Ubuntu-MozillaFirefox4.0Beta10', 'frmPurcell:Sweeterthanroses-S.McNair/TheAcademyofAncientMusic/C.Hogwood(RadioClassique)', 'dlgMainMenu']
>>> ldtp.getobjectlist('dlgMainMenu')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/pymodules/python2.7/ldtp/client.py", line 54, in __call__
    return self.__send(self.__name, args)
  File "/usr/lib/python2.7/xmlrpclib.py", line 1575, in __request
    verbose=self.__verbose
  File "/usr/lib/pymodules/python2.7/ldtp/client.py", line 102, in request
    raise e
xmlrpclib.Fault: <Fault 8002: "'NoneType' object has no attribute '_narrow'">

ProblemType: Bug
DistroRelease: Ubuntu 11.04
Package: ldtp 2.1.0-1
ProcVersionSignature: Ubuntu 2.6.38-1.28-generic 2.6.38-rc2
Uname: Linux 2.6.38-1-generic i686
Architecture: i386
Date: Mon Jan 31 10:10:47 2011
EcryptfsInUse: Yes
PackageArchitecture: all
ProcEnviron:
 LANGUAGE=en_US:en
 PATH=(custom, user)
 LANG=en_US.utf8
 LC_MESSAGES=en_US.utf8
 SHELL=/bin/bash
SourcePackage: ldtp