records with foreignkey do not change after an edit from parent page

[pascalbarbedor@…]

I tried the example Poll choices from the tutorial and it works.
ie if i change a choice from poll page it is updated

now with this model

which seem to me is completely equivalent, any edit that concern data from rubrique page is silently ignored
but if i put wrong entry in the fields i still have the error page.

SUPPORT_CHOICES = (
('PCS', 'PCS'),
('ROME', 'ROME'),
('FAP', 'FAP'),
('NSF', 'NSF'),
('PRODUIT', 'FORMATION'),
('TITRE', 'TITRE'),
('IDSSC', 'sous secteur'),
('FORMAC', 'formacode'),
('NAF', 'NAF'),
)

THEME_CHOICES = (
('MDT', 'Emploi, Marché du travail'),
('AFPA', 'Formations AFPA'),
('OBS', 'Observatoires'),
('CERT', 'Diplômes, Certification'),
('FC', 'Formation continue'),
)

ZONE_CHOICES = (
(1, 'France'),
(3, 'Régions'),
(7, 'Départements'),
(11, 'Zones demploi'),
(15,'Zones demploi et départements'),
(31,'Centres de formation'),
)

class Rubrique( meta.Model):

theme = meta.CharField(maxlength=150, choices=THEME_CHOICES)
rubrique = meta.CharField( 'rubrique', maxlength=50)
info = meta.TextField(maxlength=100, blank=True)
def repr(self):

return self.rubrique

class META:

admin = meta.Admin(

list_display = ( 'rubrique','theme', 'info'),

)

class Data( meta.Model):

data = meta.CharField( maxlength=15, core=True)

rubrique = meta.ForeignKey(Rubrique, edit_inline=meta.TABULAR, num_in_admin=10)

lb = meta.CharField( 'label', maxlength=60, core=True)
lc = meta.CharField('label court', maxlength=20, core=True, blank=True)
source = meta.CharField( maxlength=20, core=True, blank=True)
table = meta.CharField( maxlength=20, core=True, blank=True)
tfield = meta.CharField( maxlength=20, core=True, blank=True)
support = meta.CharField(maxlength=15, choices=SUPPORT_CHOICES, core=True, blank=True)

zones = meta.IntegerField( maxlength=20, choices=ZONE_CHOICES, core=True, blank=True)
#~ class META:

#~ admin = meta.Admin(

#~ list_display = ('rubrique','data', 'lb','lc', 'source','table','tfield','support','zones'),

#~ )

def repr(self):

return "%s [%s]" % (self.lb, self.data)