losing session variable

Hi, I have the following code : session_start();

    $_SESSION['username']=$myusername;
    $_SESSION['Localization'] = $lang;
    header("Location:

https://".$_SERVER['SERVER_NAME'].$path_adm_files."/modules/welcome/welcome.php");

if i check before header command what is the value of $_SESSION['username'], i get the right value. however, if i place on the first line of welcome.php file the following code : echo "<br>1. Before session";

session_start(); echo"<br>Username : ".$_SESSION['username']; echo "<br>2. After session";

i get empty value for this session variable. How is it possible ? in my first code piece, if i use localhost instead of $_SERVER['SERVER_NAME'], it creates a session file in my temporary folder as it should be.... I'm confused now :-( thanks a lot for your help. -- Alain ------------------------------------ Windows XP SP2 PostgreSQL 8.1.4 Apache 2.2.4 PHP 5.2.1