System.Runtime.InteropServices.COMException - Błąd przy wczytywaniu Excela

 private void otworzPlik_Click(object sender, EventArgs e)
        {
            OpenFileDialog okienko = new OpenFileDialog();
            okienko.Filter = "Pliki excel (xlsx)|*.xlsx";
            if (okienko.ShowDialog() == DialogResult.OK)
            {
                MessageBox.Show("Wybrano plik: " + okienko.FileName);
            }

            Excel.Application xlApp;
            Excel.Workbook xlWorkBook;
            Excel.Worksheet xlWorkSheet;
            object misValue = System.Reflection.Missing.Value;

            xlApp = new Excel.Application();
            xlWorkBook = xlApp.Workbooks.Open(okienko.FileName, 0, true, 5, "", "", true, Excel.XlPlatform.xlWindows, "\t", false, false, 0, true, 1, 0);
            xlWorkSheet = (Excel.Worksheet)xlWorkBook.Worksheets.get_Item(1);

xlApp = new Excel.Application();