Binding two tables on update - SQL Server 2008

//This code raises an foreign key violation error on the people table.

private void masterTableBindingNavigatorSaveItem_Click(object sender, EventArgs e)
        {
            this.Validate();
            this.masterTableBindingSource.EndEdit();
            this.peopleBindingSource.EndEdit();
            this.tableAdapterManager.UpdateAll(this.clientsDS);

        }
//this code corrects problem, but shouldn't be necessary.

private void peopleDataGridView_Enter(object sender, EventArgs e)
        {
            this.Validate();
            this.masterTableBindingSource.EndEdit();
            this.masterTableTableAdapter.Update(clientsDS.MasterTable);
        }