GalleryEmbed::init() returns NULL. WTF?

Hi all,

maybe someone can help me out with this one:

GalleryEmbed::init() keeps returning NULL.

I initialisied with:
$ret = GalleryEmbed::init(array('embedUri' => $embedUri,
'g2Uri' => $g2Uri,
'activeUserId' => $emAppUser['Id'],
'gallerySessionId' => session_id()));

vars:
$embedUri = '/gallery2/sometestpage.php';
$g2Uri = '/gallery2/';
$emAppUser['Id'] = ''; (as Guest)

I suppose Guest-Login should be common. What's wrong?

Please help!
Thanks a lot