Compact Framework c#: Dataset DataRow.get fails during export

I am doing a small application which handles data via a dataset. I can save the dataset to a xml file without any problem using dsetDB.WriteXml (strXMLFile). But I also need an export to a tab delimited file.

The problem is, that I always get an exception ArgumenException at about 1024bytes are read!
I have tried using string instead of stringbuilder, I have tried different versions of streams. No success.

Interestingly, the progressbar always runs up to the end of all rows (means: it looks like all rows are read), but when the exception occurs, the i counter says 34.
The file always ends up with under 1024 bytes written.

I tried many, many different approachs, ie I wrote line by line to the file, field by field, build all into one stringbuilder string and then write: no chance. The code always breaks with the same no leading exception.

The full source is available at www.hjgode.de/dotnet/InventurNet1.zip
You must undef Intermec, to run in emulation. The xml file should be placed into the same dir as the executable, as the app will only look there for the xml file to read.

The code lines are:

private void ExportText(string strFile)
{
      string strTemp = "";
      System.Text.StringBuilder strLine = new System.Text.StringBuilder();
      string delimStr = "\t";
      char [] delimiter = delimStr.ToCharArray();

      //StreamWriter srdrFile = File.CreateText (strFile);
      StreamWriter srdrFile = new StreamWriter(strFile,false, System.Text.Encoding.Default ,64);
      srdrFile.AutoFlush = true;

      //(new FileStream(strFile, FileMode.Create , FileAccess.ReadWrite ));
      //UnbindControls();
      //DisableControls();
      Cursor.Current = Cursors.WaitCursor ;
      Application.DoEvents();
      FileInfo fi=new FileInfo(strFile);
      long fileLen=fi.Length;
      pb.Maximum=dtabInventur.Rows.Count ;
      pb.Minimum=0;
      pb.Visible=true;
      dtabInventur.DefaultView.RowFilter=String.Empty ;
      DataRow drowInventur;
      try
      {
            for (int i=0; i< dtabInventur.Rows.Count-1; i ++)
            {
                  drowInventur = dtabInventur.Rows[i] ;

                  strTemp="";
                  strTemp =  drowInventur[0].ToString() + delimStr;
                  strTemp += drowInventur[1].ToString() + delimStr;
                  strTemp += drowInventur[2].ToString() + delimStr;
                  strTemp += drowInventur[3].ToString() + delimStr;
                  strTemp += drowInventur[4].ToString() + delimStr;
                  strTemp += drowInventur[5].ToString() + delimStr;
                  strTemp += drowInventur[6].ToString() ;

                  srdrFile.WriteLine(strTemp);
                  pb.Value += i ;
                  srdrFile.Flush ();

                  Application.DoEvents();
            }
      }
      catch (Exception wf)
      {
            MessageBox.Show(wf.Message + "\n" + wf.ToString(), "Uuuups");
      }
      finally
      {

            srdrFile.Flush();
            Application.DoEvents();
            pb.Visible=false;
            Cursor.Current=Cursors.Default ;

            srdrFile.Close ();
            //BindControls();
            //EnableControls();

      }
}