Error while open and close a form

//Here is the code for first page :-
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Speech.Recognition;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
      public Form1()
      {
        InitializeComponent();
      }
    
      
      private void Form1_Load(object sender, EventArgs e)
      {
        SpeechRecognizer sp = new SpeechRecognizer();
        Choices m = new Choices();
        m.Add("next");
        GrammarBuilder gb = new GrammarBuilder();
        gb.Append(m);
        Grammar g = new Grammar(gb);
        sp.LoadGrammar(g);
        sp.SpeechRecognized+=new EventHandler<SpeechRecognizedEventArgs>(sp_SpeechRecognized);
      }
      void sp_SpeechRecognized(object sender,  SpeechRecognizedEventArgs e)
      {
        if (e.Result.Text == "next")
        {
          button1.PerformClick();
        }
      }

      private void button1_Click(object sender, EventArgs e)
      {
        Form2 f2 = new Form2();
        f2.Show();
      }
    }
}
//Here is code for next form :-
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Speech.Recognition;

namespace WindowsFormsApplication1
{
    public partial class Form2 : Form
    {
      public Form2()
      {
        InitializeComponent();
      }

      private void Form2_Load(object sender, EventArgs e)
      {
        SpeechRecognizer spr = new SpeechRecognizer();
        Choices m = new Choices();
        m.Add("back");
        GrammarBuilder gb = new GrammarBuilder();
        gb.Append(m);
        Grammar g = new Grammar(gb);
        spr.LoadGrammar(g);
        spr.SpeechRecognized += new EventHandler<SpeechRecognizedEventArgs>(spr_SpeechRecognized);
      }
      void spr_SpeechRecognized(object sender, SpeechRecognizedEventArgs e)
      {
        if (e.Result.Text == "back")
        {
          button1.PerformClick();
        }
        
      }

      private void button1_Click(object sender, EventArgs e)
      {
        Form1 f = new Form1();
        f.Show();
      }
    }
}
//But when we debug it, then it shows error as a exception. What is solution????

Can you tell me, Actual error message you are receiving

Actual error message is exception of type " refraction or Target " in application form while running form1.......