Exception w/ Threading and Invoke in a Class

Option Explicit On
Option Strict On

Imports System.Text
Imports System.Net
Imports System.Net.Sockets
Imports System.Threading

Public Class clsSock
    Inherits Control

    Private Sock As Socket
    Private sName As String, sHost As String, sPort As Integer, sConnected As Boolean

    Public Event Connected(ByVal sockname As String)
    Public Event Read(ByVal sockname As String, ByVal sockread As String)

    Delegate Sub onRead(ByVal msg As String)
    Private _onRead As onRead

    Dim tdReadSock As Thread

    Public Sub New()
        _onRead = New onRead(AddressOf RaiseRead)
    End Sub

    Public Sub Open(ByVal name As String, ByVal host As String, ByVal port As Integer)
        'define endpoint, connect socket
        Dim ipHost As IPHostEntry = Dns.GetHostEntry(host)
        Dim ipEnd As New IPEndPoint(ipHost.AddressList(0), port)
        Sock = New Socket(ipEnd.Address.AddressFamily, SocketType.Stream, ProtocolType.Tcp)
        Sock.Connect(ipEnd)

        'assign local variables
        sName = name
        sHost = host
        sPort = port
        sConnected = True

        'raise an event for connection success
        RaiseEvent Connected(name)

        'start new thread for socket reading to prevent application freezing from STA
        tdReadSock = New Thread(New ThreadStart(AddressOf sockMonitor))
        tdReadSock.Start()
    End Sub

    Public Sub Send(ByVal sockdata As String)
        Dim data() As Byte = ASCIIEncoding.UTF8.GetBytes(sockdata & vbCrLf)
        Sock.Send(data, data.Length, SocketFlags.None)
    End Sub

    Private Sub sockMonitor()
        'loop while sock is connected, wait for receive, raise event for read
        Do While Sock.Connected = True
            Dim data(4096) As Byte

            Sock.Receive(data)
            Dim msg As String, msgs() As String = ASCIIEncoding.UTF8.GetString(data).Trim(Chr(0)).Split(CChar(vbCrLf))

            For Each msg In msgs
                If msg.Length > 0 Then BeginInvoke(_onRead, New Object() {msg})
            Next
        Loop
    End Sub

    Private Sub RaiseRead(ByVal msg As String)
        RaiseEvent Read(sName, msg)
    End Sub
End Class

Private WithEvents Socks As clsSock

Private Sub Sock_Connected(ByVal state As String) Handles Socks.Connected
    MsgBox("Connected - " & state)
    Socks.Send("/GET etc etc etc")
End Sub
Private Sub Sock_Read(ByVal sockname As String, ByVal sockread As String) Handles Socks.Read
    Text1.AppendText(sockname & " - " & sockread & vbCrLf)
End Sub
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
    Socks = New clsSock()
    Socks.Open("google", "google.com", 80)
End Sub