System.ObjectDisposedException: Доступ к ликвидированному объекту невозможен - C# (234898)

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.Diagnostics;
using System.IO;
using System.Configuration;
using System.Collections.Specialized;
using TechLifeForum;
using System.Threading;
 
namespace WindowsFormsApplication44
{
 
    public partial class Form4 : Form
    {
        IrcClient client;
 
        public string a;
        public Form4()
        {
            InitializeComponent();
            txtName.ReadOnly = true;
            this.MouseDown += new MouseEventHandler(Form4_MouseDown);
        }
 
        void Form4_MouseDown(object sender, MouseEventArgs e)
        {
            base.Capture = false;
            Message m = Message.Create(base.Handle, 0xa1, new IntPtr(2), IntPtr.Zero);
            this.WndProc(ref m);
        }
 
        private void Form4_Load(object sender, EventArgs e)
        {
           btnConnect_Click(sender, e);            
        }

        private delegate void _UpdateUsers(string[] userlist);
        private void UpdateUsers(string[] userlist)
        {
            #region CrossThreadCheck
            if (InvokeRequired)
            {
                this.Invoke(new _UpdateUsers(UpdateUsers), (object)userlist);
                return;
            }
            #endregion
 
            lstNames.Items.Clear();
            foreach (string u in userlist)
                lstNames.Items.Add(u);
        }// UpdateUsers
 
        private void UserJoined(string user)
        {
            ShowMessage("*" + user + " присоединился к комнате чата");
        }// UserJoined
        private void UserLeft(string user)
        {
            ShowMessage("*" + user + " покинул комнату чата");
        }// UserLeft
 
        private void ChannelMessage(string user, string message)
        {
            ShowMessage("<" + user + ">: " + message);
        }// ChannelMessage
        private void NoticeMessage(string user, string message)
        {
            ShowMessage("<--Заметка--> " + user + ": " + message);
        }// NoticeMessage
        private void PrivateMessage(string user, string message)
        {
            ShowMessage("<--Личное сообщение--> от " + user + ">: " + message);
        }// PrivateMessage
 
        private delegate void _ShowMessage(string message);
        private void ShowMessage(string message)
        {
            #region CrossThreadCheck
            if (InvokeRequired)
            {
                this.Invoke(new _ShowMessage(ShowMessage), message);
                return;
            }
            #endregion
 
            rtbWindow.AppendText("\n" + message);
            rtbWindow.ScrollToCaret();
        }

        private void Connect()
        {
            // connect to the irc server
            client.Connect("#LittleHlp");
        }// Connect
        private void txtSend_KeyPress(object sender, KeyPressEventArgs e)
        {
            if (e.KeyChar == 13) // enter key
            {
                e.Handled = true;
                btnSend_Click(sender, e);
            }
        }

        private void AddEvents()
        {
            // Save settings event
 
            // events triggered by the client
            client.UpdateUsers += new UpdateUserListEventDelegate(UpdateUsers);
            client.UserJoined += new UserJoinedEventDelegate(UserJoined);
            client.UserLeft += new UserLeftEventDelegate(UserLeft);
            client.ChannelMessage += new ChannelMesssageEventDelegate(ChannelMessage);
            client.NoticeMessage += new NoticeMessageEventDelegate(NoticeMessage);
            client.PrivateMessage += new PrivateMessageEventDelegate(PrivateMessage);
            client.Disconnected += new DisconnectedEventDelegate(Disconnect);
            client.ServerMessage += new ServerMessageEventDelegate(ShowMessage);
        }// AddEvents
 
        private void timer1_Tick(object sender, EventArgs e)
        {
            usrNum.Text = lstNames.Items.Count.ToString();
        }
 
        private void pictureBox1_Click(object sender, EventArgs e)
        {
            Disconnect();
            this.Close();
        }
 
        private void pictureBox2_Click(object sender, EventArgs e)
        {
            this.WindowState = FormWindowState.Minimized;
        }
 
        private void pictureBox1_MouseEnter(object sender, EventArgs e)
        {
            pictureBox1.Image = Properties.Resources.Close;
        }
 
        private void pictureBox1_MouseLeave(object sender, EventArgs e)
        {
            pictureBox1.Image = Properties.Resources.Clos;
        }
 
        private void pictureBox2_MouseEnter(object sender, EventArgs e)
        {
            pictureBox2.Image = Properties.Resources.m2;
        }
 
        private void pictureBox2_MouseLeave(object sender, EventArgs e)
        {
            pictureBox2.Image = Properties.Resources.m1;
        }
 
        private void btnSend_Click(object sender, EventArgs e)
        {
            if (chkRaw.Checked)
            {
                client.SendRAW("PRIVMSG " + txtName.Text + " " + txtSend.Text.Trim());
                ShowMessage("<--Личное сообщение--> к " + txtName.Text + ">: " + txtSend.Text);
            }
            else
            {
                client.SendMessage(txtSend.Text.Trim());
                ShowMessage("<" + client.Nick + ">: " + txtSend.Text);
            }
            txtSend.Clear();
            txtSend.Focus();
        }
 
        private void btnConnect_Click(object sender, EventArgs e)
        {       
            Disconnect();
            Form2 main = this.Owner as Form2;
            a = main.label1.Text;
            if (a == "Chesko")
   
                {
                    txtName.ReadOnly = false;
                    txtSend.Text = "";
                    txtName.BackColor = System.Drawing.SystemColors.Window;
                    txtName.ForeColor = System.Drawing.SystemColors.WindowText;
                }
            if (client != null)
            {
                client.Disconnect();
                return;
            }
 
            client = new IrcClient("zoidberg.centralchat.net", 6667);
            client.Nick = a;
            AddEvents();
            Thread t = new Thread(Connect);
            t.IsBackground = true;
            t.Start();
            btnSend.Visible = true;
        }
 
        private void lstNames_SelectedIndexChanged(object sender, EventArgs e)
        {
            
            string name = lstNames.SelectedItem.ToString();
            if (name.IndexOf("@") >-1  | name.IndexOf("~") >-1)
            {
                txtName.Text = name.Remove(0, 1);
            }
            else
            {
                txtName.Text = name;
            }
            if (name == "@ChanServ")
            {
                txtName.Text = "";
                MessageBox.Show("Невозможно отправить личное сообщение данному пользователю");              
            }
            
        }
 
        private void Disconnect()
        {
            if (client != null)
            {
                client.Disconnect();
                client = null;
            }
        }
    }
}