i am getting and error message "Invalid cursor state" from sql while deleting data in the resultset

public void sales_reduce()
{
    boolean notify = true;
    try
        {
        int qty = 0,billed_qty = 0;
        Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
        Connection con = DriverManager.getConnection("jdbc:odbc:fraiserDB");
        Statement s = con.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,ResultSet.CONCUR_UPDATABLE);
        ResultSet rs;
        for(int i=0; i<50; i++)
        {
        rs = s.executeQuery("select billed_qty from sales_order,Grand_total_client where batch_no = '"+t.getValueAt(i, 1).toString()+"' and Grand_total_client.invoice_no = sales_order.invoice_no  and client_id = " + id);
        rs.afterLast(); //Every time move after the last position of resultset
        rs.previous(); // moves to the last data in the resultset
        qty = Integer.parseInt(t.getValueAt(i,5).toString());
        billed_qty = rs.getInt(1);
        while(qty != 0)
        {
        if(qty < billed_qty)
        {
            rs.updateInt("billed_qty", billed_qty-qty);
            rs.updateRow();
            JOptionPane.showMessageDialog(null, "Database updated","Database updated",JOptionPane.INFORMATION_MESSAGE);
            break;
        }
        else // if qty is greater than it will zero the current stock and
        {
            qty = qty - billed_qty;
            //rs.updateInt("billed_qty", 0);
            rs.deleteRow();
            rs.previous();
            billed_qty = rs.getInt(1); // Error coming in this row
        }
        }
        rs.close();
        }
        }
        catch(NullPointerException e) {}
        catch(ClassNotFoundException e)
        {
            JOptionPane.showMessageDialog(null, "Class Not Found","SQL Exception",JOptionPane.ERROR_MESSAGE);
        }
        catch(SQLException e)
        {
            JOptionPane.showMessageDialog(null, e.getErrorCode() +" "+ e.getMessage(),"SQL Exception",JOptionPane.ERROR_MESSAGE);
        }
    if(!notify)
        JOptionPane.showMessageDialog(null, "Sales order removed","Database Updated",JOptionPane.INFORMATION_MESSAGE);
}