Problème de lancement de Thread sur PC d'un ami.

Thread th = null;

// .... Plus Loin ...

th = new Thread(new ThreadStart(Th));
th.Start();

private void Th()
{

foreach(string[] Profil in ActiveAccount)
{

ArrayList Words = CreateWordsList(Searches,new ArrayList());
status.Text = "Connection";
account.Text = Profil[0];
string prof = Profil[0];

if(prof.Length > 8) prof = prof.Substring(0,8);
ActualizeNotifyText(0,"("+prof+") : Activé");

WebBrowserA.Navigate(Urls[0], ref empty, ref empty, ref empty, ref empty);
WaitFor(ref DocLoadedA);

HTMLDocumentClass docA = WebBrowserA.Document asHTMLDocumentClass;

if(docA.body.innerHTML.IndexOf("Login") != -1)
{

// Connection
HTMLInputElement User =docA.all.item("nbuser",null) as HTMLInputElement;
HTMLInputElement Pass =docA.all.item("nbpass",null) as HTMLInputElement;
HTMLInputElement Submt =docA.all.item("login",null) as HTMLInputElement;

User.value = Profil[0];
Pass.value = Profil[1];
Submt.click();

WaitFor(ref DocLoadedA);
status.Text ="Attente";
Random ran = new Random();
Th.Join(new TimeSpan(0,0,ran.Next(2,5)+15));

}

WebBrowserA.Navigate(Urls[2], ref empty, ref empty, ref empty, ref empty);
WaitFor(ref DocLoadedA);

}

// Arrêt
button1.Text = "Lancer Sélection";
status.Text = "Désactivé";
account.Text = "Aucun";
searches.Text = "0";
ActualizeNotifyText(0," : Terminé");

}