AJAX-Upload not calling onComplete when completed

Question

NOTICE: I have read through This question which is almost the same.

I am currently uploading an image with AjaxUpload.js which works fine. The file gets uploaded BUT the onComplete never gets called.

The tutorial I followed was this one: http://www.zurb.com/playground/ajax_upload

My code is the same, except for what happens in the onSubmit & onComplete functions.

Here is what I use in my $(document).ready()

new AjaxUpload('imageUpload', {
    action: $('form#imageUploadForm').attr('action'),
    name: 'image',
    onSubmit: function(file, extension)
    {
        $('div.popupwindowlogo').children().hide();
        $('div.popupwindowlogo').append('<img class="popupwindowlogoimage temp" src="images/loading.gif"><div class="center temp">Uploading...</div>'); //IS LOADING indicator
    },
    onComplete: function(file, response)
    {
        alert("FINISHED");
    }
});

As you can guess, "FINISHED" never gets alerted to me.

Take note, I am not returning "false" as response to the upload.

Is there anything I could have missed?

Thanks!