I use this code to save a new word to my database :

Code:
private void btnOpslaan_Click(object sender, EventArgs e)
        {
            System.Data.SqlClient.SqlCommandBuilder cb;
            cb = new System.Data.SqlClient.SqlCommandBuilder(da);

            DataRow dRow = ds1.Tables["Woorden"].NewRow();

            dRow[1] = txtWoord.Text;

            ds1.Tables["Woorden"].Rows.Add(dRow);

            iMaxRows++;
            iIndex = iMaxRows - 1;

            try
            {
                da.Update(ds1, "Woorden");
            }
            catch (DBConcurrencyException ex)
            {
                string customErrorMessage;
                customErrorMessage = "Concurrency violation\n" + ex.ToString();
                MessageBox.Show(customErrorMessage);

                // Add business logic code to resolve the concurrency violation...
                return;
            }

            MessageBox.Show("Nieuw woord toegevoegd aan de database.");

            btnOpslaan.Enabled = false;
            btnVerwijderen.Enabled = true;
            btnNieuw.Enabled = true;
            btnAnnuleren.Enabled = false;
            txtWoord.Enabled = false;

            ReloadDatabase();
        }
When I close my application and reopen it, my database has the new word in it, but after reopening and closing the application a few times, suddenly the database is to it's old state again?!? What's happening?