dip item inconsistent

Tak jsem to nějak vytvořil.. ale mám problém..
používám

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    internal class C_Logger // singletonově napsaná
    {
        //private DataTable dataTable;
        private ObservableCollection<LogMessageRow> itemList;

        public void LOG(string _src, string _msg)
        {
            itemList.Add(new LogMessageRow { src = _src, msg = _msg });
        }

        // property
        public ObservableCollection<LogMessageRow> Data
        {
            get { return itemList; }
        }

    }

    public class LogMessageRow
    {
        public string src { get; set; }
        public string msg { get; set; }
    }

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
.. a potom v main.xaml

        <DataGrid
              DataContext="{StaticResource ItemCollectionViewSource}"
              ItemsSource="{Binding}"
              AutoGenerateColumns = "False"
              CanUserAddRows="False"
            >
            <DataGrid.Columns>
                <DataGridTextColumn Header="Source" IsReadOnly="True"  Binding="{Binding Path=src}" Width="50"></DataGridTextColumn>
                <DataGridTextColumn Header="Message" IsReadOnly="True"  Binding="{Binding Path=msg}" MinWidth="50" ></DataGridTextColumn>
            </DataGrid.Columns>
        </DataGrid>

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
a v main.cs binding

    public MainWindow()
    {
        InitializeComponent();

            // link business data to CollectionViewSource
            CollectionViewSource itemCollectionViewSource;
            itemCollectionViewSource = (CollectionViewSource)(FindResource("ItemCollectionViewSource")); // jenom abych nemusel davat nazev (odněkud zkopčeno)
            itemCollectionViewSource.Source = C_Logger.Instance.Data;

    }


    private void Button_Click(object sender, RoutedEventArgs e)
    {
        C_Logger.Instance.LOG_gui("GUI","SOMETHING HAPPENED"); // funguje normálně přidá
    }


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
SPI (napsany jenom tak..)

    internal class C_SPI
    {

        private static object locker = new object();
        private static SerialPort spi;

        public static bool WriteData(byte[] data)
        {
            lock (locker)
            {
                int q = 10; // try q-times
                while (q>0)
                {
                    if (spi.IsOpen)
                    {
                        WriteSerialPort(data);
                        return true;
                        //responseBuffer = ReadSerialPort(8);
                    }
                    else
                    {
                        OPEN_connection();
                    }
                    q--;
                }
            }
            return false; // should never run as far as to this line
        }


        private static void WriteSerialPort(byte[] data)
        {
            //spi.Write(data, 0, data.Length);
            C_Logger.Instance.LOG_spi("SPI HAPPENED"); // tohle je to co se mu nelíbí
        }
    }

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
motor
    internal class C_Motor
    {

        public void SEND_cmd(byte[] cmd)
        {
            BackgroundWorker worker = new BackgroundWorker();
            worker.RunWorkerCompleted += worker_RunWorkerCompleted;
            worker.DoWork += worker_DoWork;

            //SEND_cmd_eventArgs args = new SEND_cmd_eventArgs(id, cmd);
            DoWorkEventArgs args = new SEND_cmd_eventArgs(id, cmd);
            worker.RunWorkerAsync(args);
        }

        private void worker_DoWork(object sender, DoWorkEventArgs e)
        {
            byte[] b = new byte[0];
            e.Result = C_SPI.WriteData(b);
        }

        private void worker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
        {
            // catch if response was A-OK
            if (e.Error != null)
            {
                C_Logger.Instance.LOG_motX_e(id,String.Format("{0}:\n{1}",e.Error.Data ,e.Error.Message));
            }
            else
            {
                C_Logger.Instance.LOG_mot("DATA SENT");
                //var results = e.Result as List<object>;
            }
        }
    }


// no ale nejde mi dyž zavolám tu fci LOG když jsem v SPI writing funkci (respektive že ju volám v tom Background workeru)
no a ona se nepřidá do datagridu..
a když pak zkusim přidat item zase tlačítkem, tak mi zahlásí že ten binding není stejnej na obou stranách - jakokdyby se nevyvolala změna dyž jsem v jiném threadu

An item control is inconsistent with its source

řešení:
1) to musím ošetřit volání pro změnu v tom ObservableCollectionu zavolat event sám?
2) nevolat v tom novém threadu vůbec LOG, ale pouze např vyčíst zpětnou hodnotu background workera a do logu zapsat potom co se z něj vrátím?
3) je to v tom že binduju ObservableCollection<LogMessageRow> itemList; na DataGrid ? a nemam tam ten DataTable jak jsi říkal původně?


esi to z toho nejde pochopit, tak udělám nějaký minimum example a pošlu :)