Hello everybody!!!!!

Friends, when i try to open a new session of sale i get this error:

Traceback (most recent call last): File "/opt/openerp/openerp/http.py", line 544, in _handle_exception return super(JsonRequest, self)._handle_exception(exception) File "/opt/openerp/openerp/http.py", line 581, in dispatch result = self._call_function(**self.params) File "/opt/openerp/openerp/http.py", line 317, in _call_function return checked_call(self.db, *args, **kwargs) File "/opt/openerp/openerp/service/model.py", line 154, in wrapper raise openerp.osv.orm.except_orm(_('Integrity Error'), msg) except_orm: ('Integrity Error', 'The operation cannot be completed, probably due to the following:\n- deletion: you may be trying to delete a record while other records still reference it\n- creation/update: a mandatory field is not correctly set\n\n[object with reference: Product - product.product]')

Can anyone help me please