Tony - I would
think that the cookie domain should still be set to .yoursite.com, but I don't know that much about the way cookies and subdomains work. You may want to search vb.com or here for something like "cookie domian subdomain" and you can probably find a better answer.
350Chevy - I knew I should have mentioned how to do that too since it makes more sense to do it that way... All you'd do is look for this line in the threads section:
PHP Code:
if ($showthreaddate) {
$thread['time'] = vbdate($timeformat, $thread['dateline']);
$thread['date'] = date("m-d-y", $thread['dateline']);
You would just change 'dateline' at the end of both of those lines to 'lastpost'.