[Moo] Using form.request does not return response?

[websam]

I'm using the following codesnipet to send a form:

$('submit').addEvent('click', function (e) {
    e.stop();

    var errorLabel = $$('.lbl_error');
    var request = new Form.Request(form, errorLabel, {
        resetForm: false,
        extraData: {
            'content': tinyMCE.activeEditor.getContent()
        },
        onSuccess: function (resp) {
            alert(resp);
        }
    });
    request.send();
});

However the line alert(resp); returns null even when i see the
returned text in firebug. What am I doing wrong here?

/Martin