Shadowbox con prototype

[bonzox]

Ho dei problemi a far fuzionare shadowbox con prototype

<script type="text/javascript" src="/src/js/lib/prototype.js"></script>
<script type="text/javascript" src="/src/js/lib/scriptaculous.js?load=effects"></script>
<script type="text/javascript" src="/src/js/adapter/shadowbox-prototype.js"></script>
<script type="text/javascript" src="/src/js/shadowbox.js"></script>

<script type="text/javascript">

document.observe('dom:loaded', function(){

    Shadowbox.init({
        skipSetup: true // skip the automatic setup
    });

    // set up all anchor elements with a 'movie' class to work with Shadowbox
    Shadowbox.setup($$('a.movie'), {
        gallery:            'My Movies',
        autoplayMovies:     true
    });

});

</script>-->

errore:

document.observe is not a function
[Break on this error] document.observe('dom:loaded', function(){

Il codice è quello che da il sito di shadowbox...