admin login problems and 'ValidationError: [u'ManagementForm data is missing or has been tampered with'] '

veral times, until eventually it fails with ValidationError: [u'ManagementForm data is missing or has been tampered with'] It does not matter what project, app or model they are going to. It's not even the same admin's... it's actually spread across several projects/sites

ValidationError: [u'ManagementForm data is missing or has been tampered with']

I have this model: http://dpaste.com/111206/ and this admin.py: http://dpaste.com/111207/ but when I try to edit an existing "Impresa" i get a ValidationError: ManagementForm data is missing or has been tampered with what's the problem? -- Alessandro Ronchi Skype: aronchi http://www.alessandro