[exceem]

been getting a few php errors in my error log:

error is
PHP Fatal error: Class 'vBulletinHook' not found in /home/trevor/public_html/forums/includes/functions.php on line 4322

I think its reffering to this bit of code

function exec_header_redirect($url)
{
	global $vbulletin;

	$url = create_full_url($url);

	if (class_exists('vBulletinHook'))
	{
		// this can be called when we don't have the hook class
		($hook = vBulletinHook::fetch_hook('header_redirect')) ? eval($hook) : false;
	}

	$url = str_replace('&', '&', $url); // prevent possible oddity

	if (SAPI_NAME == 'cgi' OR SAPI_NAME == 'cgi-fcgi')
	{
		header('Status: 301 Moved Permanently');
	}
	else
	{
		header('HTTP/1.1 301 Moved Permanently');
	}

	header("Location: $url");
	define('NOPMPOPUP', 1);
	if (defined('NOSHUTDOWNFUNC'))
	{
		exec_shut_down();
	}
	exit;
}

the redirects for me visiting a archieved link works taking me to a "proper" thread

im checking my logs now to see if its not working the other way around, any ideas as to whats causing this error?