Alright, so I finally got around to testing this out, and it's still not working.
I've done some work on the situation, and I'm convinced that it's not an issue with the cache. The problem is that the cookie is simply not being deleted. I tried it out --- logged in, tried logging out, and viewed my cookies. It was still there.
I then manually cleared my cookies. From that point on, I was able to seamlessly log in and log out as I pleased. THAT is the troubling part for me.... that for the same user, without any changes to the page's content, different things happen.
The logout script is as follows:
setcookie("account", "", 1);
header( 'Location: http://www.sbboard.com/auslander/home.php ');