Works for me with build 2004-08-17-09, Windows XP. When I loaded the page, 2 seconds later I got a "!" in the lower right of my Mozilla build showing me it had blocked the popup.
WFM: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.2) Gecko/20040817 Firefox/0.9.1+
see bug 187255 comment 1 *** This bug has been marked as a duplicate of 187255 ***