OleDbDataAdapter: cannot update database

Question

I've been working on this since yesterday and I just can't update my database. There are 3 tables. Here is a piece of code of one of WinForms. It loads data and display but after changing sth manually in the grid I get either errors by calling Update or anything happens at all.

please help because I'm going crazy.

    public partial class Form3 : Form
    {
    //instance fields
    private export2Excel export2XLS;
    private DataSet _dataSet;
    private BindingSource _bsrc;
    private OleDbDataAdapter _dAdapter;
    private OleDbCommandBuilder _cBuilder;
    private DataTable _dTable;

    private void button1_Click(object sender, EventArgs e)
    {
        //create the connection string
        string connString = "Provider=Microsoft.Jet.OLEDB.4.0;Data      
        Source='C:\\Documents and Settings\\dorota\\Moje dokumenty\\Visual Studio  
        2010\\Projects\\WindowsFormsApplication1\\WindowsFormsApplication1\\artb.mdb'";

        //create the database query
        string query = "SELECT * FROM Samochody";
        System.Data.DataSet DtSet = new System.Data.DataSet();
        _dataSet = DtSet;
        //create an OleDbDataAdapter to execute the query
        OleDbDataAdapter dAdapter = new OleDbDataAdapter(query, connString);
        dAdapter.FillSchema(_dataSet, SchemaType.Source);

        _dAdapter = dAdapter;
        //create a command builder
        OleDbCommandBuilder cBuilder = new OleDbCommandBuilder(_dAdapter);
        _cBuilder = cBuilder;
        //create a DataTable to hold the query results
        DataTable dTable = new DataTable();
        _dTable = dTable;
        //fill the DataTable
        _dAdapter.Fill(_dTable);
        //_dAdapter.TableMappings.Add("Samochody", "Table");

        _dAdapter.Fill(_dataSet);

        // --------------------- to datagridview !

        //BindingSource to sync DataTable and DataGridView
        BindingSource _bsrc = new BindingSource();

        //set the BindingSource DataSource
        //bSource.DataSource = _dTable;
        _bsrc.DataSource = _dTable;
        //_bsrc = bSource;
        //set the DataGridView DataSource
        dataGridView1.DataSource = _bsrc;
    }
    }

and here... :

    private void sqlsave_Click(object sender, EventArgs e)
    {

        //int i=_dAdapter.Update(_dTable);
        _dAdapter.Update(_dataSet.Tables["Samochody"]);
        //_dAdapter.Update(_dataSet,"Samochody");
    }

//---------------------------------------------------------------------------------

ok. I have changed sqlsave method for this

    private void sqlsave_Click(object sender, EventArgs e)
    {

    try
    {
        //_dAdapter.Update(_dataSet.Tables["Samochody"]);
         OleDbCommand oldb= _cBuilder.GetUpdateCommand();
         int i=oldb.ExecuteNonQuery();
         System.Windows.Forms.MessageBox.Show(i+" rows affected.");
        //_dAdapter.Update(_dataSet,"Samochody");
    }catch(OleDbException oldbex){
        System.Windows.Forms.MessageBox.Show(oldbex.ToString());
    }

and now I get finally sth more informative than "Error in"

An unhandled exception of type 'System.InvalidOperationException' occurred in System.Data.dll Additional information: ExecuteNonQuery requires an open and available Connection. The connection's current state is closed.

so let me changed sth and I will let you know if this is it!

//--------------------------------

no. no. too fast, can't last. now while trying to save I've got exception again, connectin is opened, but (I can't post the image) when I debug this I see that my object of OleDbCommand type as _commandText has

"UPDATE Samochody SET Item=?, Data dyspozycji autem od=?, ..."

and so on. I think this is the reason. Am I right? What to do?