I am not sure how good my code is but it does work for now ...
Protected Sub DoLogin()
Dim authCookie As HttpCookie = FormsAuthentication.GetAuthCookie(UserName, False)
Dim ticket As FormsAuthenticationTicket = FormsAuthentication.Decrypt(authCookie.Value)
Dim newTicket As New FormsAuthenticationTicket(ticket.Version, ticket.Name, ticket.IssueDate, ticket.Expiration, ticket.IsPersistent, "")
authCookie.Value = FormsAuthentication.Encrypt(newTicket)
Response.Cookies.Add(authCookie)
Response.Redirect("Default.aspx", False)
End Sub