I'm not sure if this has been covered or not. But there seems to be a bug where in Firefox/mozilla browsers the videos will autoplay even if you dont' check it. You have to go to
include/inc_front/content/cnt9.article.inc.php
And on Line 33 change
$media["media_auto"] = (intval($media["media"][8])) ? "true" : "false";
to
$media["media_auto"] = (intval($media["media"][8])) ? "true" : "0";
This is for Release 1.1-RC4 27-08-2004