An exception of type 'Newtonsoft.Json.JsonSerializationException' occurred in mscorlib.ni.dll but was not handled in user code

Quote:

An exception of type 'Newtonsoft.Json.JsonSerializationException' occurred in mscorlib.ni.dll but was not handled in user code

Additional information: Error getting value from 'DisplayMemberPath' on 'MS.Internal.DisplayMemberTemplate'.

private async void InsertUser(UsersLog user)
    {
        // This code inserts a new User into the database. 
        **await Users.InsertAsync(user);**
        users.Add(user);
    }

    private void Button_Click(object sender, RoutedEventArgs e)
    {
        var userName = new UsersLog { Username = txtUserName.Text };
        if (MyPassword.Text == MyPassword1.Text)
        {
            var password = new UsersLog { Password = MyPassword1.Text };
            ListPickerItem selectedItem = this.lpkSecQuestion.ItemContainerGenerator.ContainerFromItem(this.lpkSecQuestion.SelectedItem) as ListPickerItem;
            var securityQ = new UsersLog { SecurityQuestion = selectedItem };
            var answer = new UsersLog { Answer = txtAnswer.Text };

            InsertUser(userName);
            InsertUser(password);
            InsertUser(securityQ);
            InsertUser(answer);

            //launch a form to register Owner (RegisterOwner.xaml)
            NavigationService.Navigate(new Uri("/RegisterOwner.xaml", UriKind.Relative));
        }
        else
        {                
            MessageBoxResult result = MessageBox.Show("The Password mismatch","User Account",MessageBoxButton.OKCancel);
            switch (result)
            {
                //User pressed OK button
                case MessageBoxResult.OK:
                    MyPassword.Text = "";
                    MyPassword1.Text = "";
                    MyPassword.Focus();
                    break;
            }               
        }

    }