"<Fault 4: 'Resource path is not callable.'>" error after install

If ever you have an error like this after installing both the OpenERP module and the Magento and clicking on the "Synchronize referential settings" module with such a stack trace:

[2009-10-26 15:56:35,698] INFO:Magento Connection:Calling Method:ol_websites.list,Arguments:[]
No LSB modules are available.
[2009-10-26 15:56:36,973] ERROR:Magento Call:[01]:
[2009-10-26 15:56:36,974] ERROR:Magento Call:[02]: Environment Information :
[2009-10-26 15:56:36,974] ERROR:Magento Call:[03]: System : Linux-2.6.28-15-generic-x86_64-with-Ubuntu-9.04-jaunty
[2009-10-26 15:56:36,974] ERROR:Magento Call:[04]: OS Name : posix
[2009-10-26 15:56:36,974] ERROR:Magento Call:[05]: Distributor ID: Ubuntu
[2009-10-26 15:56:36,974] ERROR:Magento Call:[06]: Description: Ubuntu 9.04
[2009-10-26 15:56:36,974] ERROR:Magento Call:[07]: Release: 9.04
[2009-10-26 15:56:36,974] ERROR:Magento Call:[08]: Codename: jaunty
[2009-10-26 15:56:36,975] ERROR:Magento Call:[09]: Operating System Release : 2.6.28-15-generic
[2009-10-26 15:56:36,975] ERROR:Magento Call:[10]: Operating System Version : #52-Ubuntu SMP Wed Sep 9 10:48:52 UTC 2009
[2009-10-26 15:56:36,975] ERROR:Magento Call:[11]: Operating System Architecture : 64bit
[2009-10-26 15:56:36,975] ERROR:Magento Call:[12]: Operating System Locale : en_US.UTF8
[2009-10-26 15:56:36,975] ERROR:Magento Call:[13]: Python Version : 2.6.2
[2009-10-26 15:56:36,975] ERROR:Magento Call:[14]: OpenERP-Server Version : 5.0.6
[2009-10-26 15:56:36,975] ERROR:Magento Call:[15]: Last revision No. & ID : 1866 <email address hidden>
[2009-10-26 15:56:36,975] ERROR:Magento Call:[16]:
[2009-10-26 15:56:36,976] ERROR:Magento Call:[17]: Method: ol_websites.list
[2009-10-26 15:56:36,976] ERROR:Magento Call:[18]: Arguments:[]
[2009-10-26 15:56:36,976] ERROR:Magento Call:[19]: Error:
No LSB modules are available.
[2009-10-26 15:56:37,350] ERROR:web-services:[01]:
[2009-10-26 15:56:37,351] ERROR:web-services:[02]: Environment Information :
[2009-10-26 15:56:37,351] ERROR:web-services:[03]: System : Linux-2.6.28-15-generic-x86_64-with-Ubuntu-9.04-jaunty
[2009-10-26 15:56:37,351] ERROR:web-services:[04]: OS Name : posix
[2009-10-26 15:56:37,351] ERROR:web-services:[05]: Distributor ID: Ubuntu
[2009-10-26 15:56:37,351] ERROR:web-services:[06]: Description: Ubuntu 9.04
[2009-10-26 15:56:37,351] ERROR:web-services:[07]: Release: 9.04
[2009-10-26 15:56:37,351] ERROR:web-services:[08]: Codename: jaunty
[2009-10-26 15:56:37,352] ERROR:web-services:[09]: Operating System Release : 2.6.28-15-generic
[2009-10-26 15:56:37,352] ERROR:web-services:[10]: Operating System Version : #52-Ubuntu SMP Wed Sep 9 10:48:52 UTC 2009
[2009-10-26 15:56:37,352] ERROR:web-services:[11]: Operating System Architecture : 64bit
[2009-10-26 15:56:37,352] ERROR:web-services:[12]: Operating System Locale : en_US.UTF8
[2009-10-26 15:56:37,352] ERROR:web-services:[13]: Python Version : 2.6.2
[2009-10-26 15:56:37,352] ERROR:web-services:[14]: OpenERP-Server Version : 5.0.6
[2009-10-26 15:56:37,352] ERROR:web-services:[15]: Last revision No. & ID : 1866 <email address hidden>
[2009-10-26 15:56:37,352] ERROR:web-services:[16]:
[2009-10-26 15:56:37,352] ERROR:web-services:[17]: Traceback (most recent call last):
[2009-10-26 15:56:37,353] ERROR:web-services:[18]: File "/home/rvalyi/DEV/openerp5.0/server/bin/osv/osv.py", line 59, in wrapper
[2009-10-26 15:56:37,353] ERROR:web-services:[19]: return f(self, dbname, *args, **kwargs)
[2009-10-26 15:56:37,353] ERROR:web-services:[20]: File "/home/rvalyi/DEV/openerp5.0/server/bin/osv/osv.py", line 119, in execute
[2009-10-26 15:56:37,353] ERROR:web-services:[21]: res = pool.execute_cr(cr, uid, obj, method, *args, **kw)
[2009-10-26 15:56:37,353] ERROR:web-services:[22]: File "/home/rvalyi/DEV/openerp5.0/server/bin/osv/osv.py", line 110, in execute_cr
[2009-10-26 15:56:37,353] ERROR:web-services:[23]: return getattr(object, method)(cr, uid, *args, **kw)
[2009-10-26 15:56:37,353] ERROR:web-services:[24]: File "/home/rvalyi/DEV/openerp5.0/addons/magentoerpconnect/magerp_core.py", line 57, in core_sync
[2009-10-26 15:56:37,353] ERROR:web-services:[25]: self.pool.get('external.shop.group').mage_import_base(cr, uid,core_imp_conn, inst.id, defaults={'referential_id':inst.id})
[2009-10-26 15:56:37,354] ERROR:web-services:[26]: File "/home/rvalyi/DEV/openerp5.0/addons/magentoerpconnect/magerp_osv.py", line 207, in mage_import_base
[2009-10-26 15:56:37,354] ERROR:web-services:[27]: data = conn.call(list_method, context['ids_or_filter'])
[2009-10-26 15:56:37,354] ERROR:web-services:[28]: File "/home/rvalyi/DEV/openerp5.0/addons/magentoerpconnect/magerp_osv.py", line 45, in call
[2009-10-26 15:56:37,354] ERROR:web-services:[29]: res = self.ser.call(self.session, method, arguments)
[2009-10-26 15:56:37,354] ERROR:web-services:[30]: File "/usr/lib/python2.6/xmlrpclib.py", line 1199, in __call__
[2009-10-26 15:56:37,354] ERROR:web-services:[31]: return self.__send(self.__name, args)
[2009-10-26 15:56:37,354] ERROR:web-services:[32]: File "/usr/lib/python2.6/xmlrpclib.py", line 1489, in __request
[2009-10-26 15:56:37,354] ERROR:web-services:[33]: verbose=self.__verbose
[2009-10-26 15:56:37,354] ERROR:web-services:[34]: File "/usr/lib/python2.6/xmlrpclib.py", line 1253, in request
[2009-10-26 15:56:37,355] ERROR:web-services:[35]: return self._parse_response(h.getfile(), sock)
[2009-10-26 15:56:37,355] ERROR:web-services:[36]: File "/usr/lib/python2.6/xmlrpclib.py", line 1392, in _parse_response
[2009-10-26 15:56:37,355] ERROR:web-services:[37]: return u.close()
[2009-10-26 15:56:37,355] ERROR:web-services:[38]: File "/usr/lib/python2.6/xmlrpclib.py", line 838, in close
[2009-10-26 15:56:37,355] ERROR:web-services:[39]: raise Fault(**self._stack[0])
[2009-10-26 15:56:37,355] ERROR:web-services:[40]: Fault: <Fault 4: 'Resource path is not callable.'>

The problem might be that Magento loaded your modules but didn't reload all the new webservices it defines.
The solution is to refresh the Magento cash in Magento backoffice:
System > Cache Managerement:
All cache: choose "refresh"
then refresh button

Hope this helps!