Lost Sessions

Could somebody please tell me what I am doing wrong.

I have spent that past couple of days chasing an intermittent session
problem where the session just gets lost and I return to the login screen.

----------------------------------------------------------------------------
----
PHP Session Code
----------------------------------------------------------------------------
----
session_start();
header("Cache-control: private"); //IE 6 Fix

if (isset($_POST['login_userid']) && isset($_POST['login_passwd']))
{
$encrypted_passwd = md5($GLOBALS['encrypt_key'] .
$_POST['login_passwd']);

$userid = $_POST['login_userid'];
$passwd = $encrypted_passwd;
}
else
{
$userid = $_SESSION['userid'];
$passwd = $_SESSION['passwd'];
}

if($GLOBALS['do'] == "logout" || !isset($userid))
{
session_unset();
session_destroy();
_display_login("Please login to access the Site Administrator.");
exit;
}

session_register("userid");
$_SESSION['userid'] = $userid;

session_register("passwd");
$_SESSION['passwd'] = $passwd;

if ($GLOBALS['site']['adminuserid'] != $userid ||
$GLOBALS['site']['adminpasswd'] != $passwd)
{
session_unset();
session_destroy();
_display_login("Bad UserID or Password!");
exit;
}

----------------------------------------------------------------------------
----

"Forcypal" <go.to.www.heyes.co.uk@for.my.email.address> wrote in
news:bfrko2$p6g$1@hercules.btinternet.com:

> I have spent that past couple of days chasing an intermittent session
> problem where the session just gets lost and I return to the login
> screen.

Are you sure that it's not just the session or cookie expiring?

KAH