Sale module does'nt work with french langage

If I try to create a new quotation with a user in French, I've got this message :

Traceback (most recent call last):
  File "/home/syleam/openerp/5.0/server/bin/netsvc.py", line 395, in run
    r = m(*msg[2:])
  File "/home/syleam/openerp/5.0/server/bin/service/web_services.py", line 387, in execute
    res = service.execute(db, uid, object, method, *args)
  File "/home/syleam/openerp/5.0/server/bin/osv/osv.py", line 107, in execute
    res = pool.execute_cr(cr, uid, obj, method, *args, **kw)
  File "/home/syleam/openerp/5.0/server/bin/osv/osv.py", line 85, in execute_cr
    return getattr(object, method)(cr, uid, *args, **kw)
  File "/home/syleam/openerp/5.0/server/bin/osv/orm.py", line 1068, in fields_view_get
    xarch, xfields = self.__view_look_dom_arch(cr, user, doc, context=context)
  File "/home/syleam/openerp/5.0/server/bin/osv/orm.py", line 861, in __view_look_dom_arch
    fields_def = self.__view_look_dom(cr, user, node, context=context)
  File "/home/syleam/openerp/5.0/server/bin/osv/orm.py", line 853, in __view_look_dom
    fields.update(self.__view_look_dom(cr, user, f, context))
  File "/home/syleam/openerp/5.0/server/bin/osv/orm.py", line 853, in __view_look_dom
    fields.update(self.__view_look_dom(cr, user, f, context))
  File "/home/syleam/openerp/5.0/server/bin/osv/orm.py", line 853, in __view_look_dom
    fields.update(self.__view_look_dom(cr, user, f, context))
  File "/home/syleam/openerp/5.0/server/bin/osv/orm.py", line 853, in __view_look_dom
    fields.update(self.__view_look_dom(cr, user, f, context))
  File "/home/syleam/openerp/5.0/server/bin/osv/orm.py", line 803, in __view_look_dom
    xarch, xfields = self.pool.get(relation).__view_look_dom_arch(cr, user, f, ctx)
  File "/home/syleam/openerp/5.0/server/bin/osv/orm.py", line 861, in __view_look_dom_arch
    fields_def = self.__view_look_dom(cr, user, node, context=context)
  File "/home/syleam/openerp/5.0/server/bin/osv/orm.py", line 853, in __view_look_dom
    fields.update(self.__view_look_dom(cr, user, f, context))
  File "/home/syleam/openerp/5.0/server/bin/osv/orm.py", line 853, in __view_look_dom
    fields.update(self.__view_look_dom(cr, user, f, context))
  File "/home/syleam/openerp/5.0/server/bin/osv/orm.py", line 853, in __view_look_dom
    fields.update(self.__view_look_dom(cr, user, f, context))
  File "/home/syleam/openerp/5.0/server/bin/osv/orm.py", line 845, in __view_look_dom
    node.setAttribute('string', trans.decode('utf8'))
  File "/usr/lib/python2.5/encodings/utf_8.py", line 16, in decode
    return codecs.utf_8_decode(input, errors, True)
UnicodeEncodeError: 'ascii' codec can't encode character u'\xe9' in position 1: ordinal not in range(128)

But with a user in english, it's ok.