Problem with is_not_guest function

[-Mirco-]

Hello guys,
i have a problem with this function.

Since morning to night i had a problem with this code:

<?php
$path ="path";
chdir($path);
require_once('SSI.php');
is_not_guest('Text message.');
$path ="/here the path";
chdir($path);

?>

Until few time ago it works well, but not now.

Now i receive a database error, problem is function, because if a comment it, i not receive error.

Error is the following
Errore del Database
Ritenta! Se riappare questa schermata, segnala il problema ad un amministratore.
Indietro

Can anyone help me?