[Lynne]

That is not a default header template, but that isn't where to look for it anyway. Look in headinclude for this at the bottom:

<script type="text/javascript" src="clientscript/vbulletin_global.js?v=$vboptions[simpleversion]"></script>
<if condition="$show['popups']"><script type="text/javascript" src="clientscript/vbulletin_menu.js?v=$vboptions[simpleversion]"></script></if>
<if condition="$vboptions['externalrss']">
<link rel="alternate" type="application/rss+xml" title="$vboptions[bbtitle] RSS Feed" href="external.php?type=RSS2" />
<if condition="$show['foruminfo'] OR $show['threadinfo']">
<link rel="alternate" type="application/rss+xml" title="$vboptions[bbtitle] - $foruminfo[title_clean] - RSS Feed" href="external.php?type=RSS2&amp;forumids=$foruminfo[forumid]" />
</if>
</if>

The line that has the if clause for showing popups. Is it there? If so, look in vboptions > Style & Language and see if Use 'vBMenu' DHTML Popup Menus? is set to Yes.