I've been testing the assignment part this morning. Upload a video as a submission is fine, but when you come to preview it (clicking the thumbnail image) the response gives a javascript error which seems to prevent the video from appearing in the lightbox popup.
Attached is a screenshot including firebug monitoring the popup appearance and error details:
Mon, 02/27/2012 - 10:37
Argh no attachment! Is this a bug in the forum code? No warnings of it being a suspected spam message :(