A machine.config error when I try to send an e-mail from an aspx page

I have an aspx page that send an email to the user, and until now it worked, but now I receive an error. This is the sub and the error:

Code:

---

Sub send_Password(Sender As Object, E As ImageClickEventArgs)
  If (Page.IsValid) Then
 
  Dim CmdPassword As New SqlCommand("return_Password", strConnection)
  CmdPassword.CommandType = CommandType.StoredProcedure
       
  CmdPassword.Parameters.Add(New SqlParameter("@e_mail", SqlDbType.varchar, 50, "e_mail"))
  CmdPassword.Parameters("@e_mail").Value = mail.Text()
 
  CmdPassword.Parameters.Add("@Resp", SqlDbType.TinyInt)
  CmdPassword.Parameters("@Resp").Direction = ParameterDirection.Output
 
  CmdPassword.Parameters.Add("@Password", SqlDbType.varchar, 8)
  CmdPassword.Parameters("@Password").Direction = ParameterDirection.Output
 
  strConnection.open()
  CmdPassword.ExecuteNonQuery
  Dim Response As byte = CmdPassword.Parameters("@Resp").Value
  strConnection.close()
 
  If (Resonse = 1) Then
    Dim E_mail As New MailMessage()
      E_mail.To = mail.Text()
          E_mail.From =  """Cesar"" <[email protected]>"
          E_mail.Subject = "Access Data - MySite.com"
          E_mail.Body = "Your access code is: " & CmdPassword.Parameters("@Password").Value   
      E_mail.Priority = MailPriority.Normal
         
          try
            SmtpMail.SmtpServer = "mail.infomail.es"
            SmtpMail.Send(E_mail)
        Response.Redirect("forgotten_code_ok.aspx")
               
          catch exc as Exception
            Message.Text() = "An error happened."
          End Try                 
 
  Else
    Message2.Text() = "None user was found with these credentials." 
  End If
 
  End If
 End Sub

---

And the server error message:
The XML file c:\winnt\microsoft.net\framework\v1.1.4322\Config\machine.config could not be loaded. Attempted to access an unloaded AppDomain.
Source Error: [No relevant source lines]

How can I solve it?

Thanks