General Printable Format error con librería wkhtmltopdf

Hola

Necesito generar el PDF del CFDI pero presenta errores.
Primero mostraba este mensaje:

******************************************************************************************************************** File "/opt/openerp/server/openerp/addons/l10n_mx_ir_attachment_facturae/ir_attachment_facturae.py", line 266, in signal_printable
    fname)
  File "/opt/openerp/server/openerp/addons/l10n_mx_facturae/invoice.py", line 136, in create_report
    (result, format) = service.create(cr, uid, res_ids, report_name, context=context)
  File "/opt/openerp/server/openerp/addons/report_webkit/webkit_report.py", line 340, in create
    result = self.create_source_pdf(cursor, uid, ids, data, report_xml, context)
  File "/opt/openerp/server/openerp/report/report_sxw.py", line 478, in create_source_pdf
    result = self.create_single_pdf(cr, uid, [obj.id], data, report_xml, context)
  File "/opt/openerp/server/openerp/addons/report_webkit/webkit_report.py", line 313, in create_single_pdf
    bin = self.get_lib(cursor, uid)
  File "/opt/openerp/server/openerp/addons/report_webkit/webkit_report.py", line 96, in get_lib
    _('Please install executable on your system' \
except_osv:(u'La ruta a la libreria Wkhtmltopdf no est\xe1 configurada', u'Por favor, instale el ejecutable en su sistema (sudo apt-get install wkhtmltopdf) o desc\xe1rguelo desde aqu\xed: http://code.google.com/p/wkhtmltopdf/downloads/list y ponga la ruta del archivo en ir.config_parameter la clave webkit_path. La versi\xf3n m\xednima es la 0.9.9')
********************************************************************************************************************

Instale la librería Wkhtmltopdf pero ahora indica lo siguiente:

********************************************************************************************************************
  File "/opt/openerp/server/openerp/addons/l10n_mx_ir_attachment_facturae/ir_attachment_facturae.py", line 266, in signal_printable
    fname)
  File "/opt/openerp/server/openerp/addons/l10n_mx_facturae_cbb/invoice.py", line 103, in create_report
    (result, format) = service.create(cr, uid, res_ids, {}, {})
  File "/opt/openerp/server/openerp/addons/report_webkit/webkit_report.py", line 340, in create
    result = self.create_source_pdf(cursor, uid, ids, data, report_xml, context)
  File "/opt/openerp/server/openerp/report/report_sxw.py", line 478, in create_source_pdf
    result = self.create_single_pdf(cr, uid, [obj.id], data, report_xml, context)
  File "/opt/openerp/server/openerp/addons/report_webkit/webkit_report.py", line 314, in create_single_pdf
    pdf = self.generate_pdf(bin, report_xml, head, foot, htmls)
  File "/opt/openerp/server/openerp/addons/report_webkit/webkit_report.py", line 177, in generate_pdf
    _("The command 'wkhtmltopdf' failed with error code = %s. Message: %s") % (status, error_message))
except_osv:('Webkit error', "The command 'wkhtmltopdf' failed with error code = 1. Message: The following diagnosis message was provided:\nThe switch --header-html, is not support using unpatched qt, and will be ignored.The switch --footer-html, is not support using unpatched qt, and will be ignored.wkhtmltopdf: cannot connect to X server \n")
********************************************************************************************************************

El modulo Motor de informes Webkit ya esta instalado.
Lo que hice fue Crear una nueva Clave en Parámetros del sistema
Clave -- webkit_path
Valor -- /usr/bin/wkhtmltopdf

Pero sigue mostrando el mismo mensaje.

De antemano muchas gracias por la ayuda