Missing slash in URL

I have the following code in the sidebar of a site I set up for some friends:

<li><h2>Events</h2>
<ul>
<?php wp_get_archives('type=monthly&cat=2&showposts=5'); ?>
</ul>
</li>

When I click on the archive link in the sidebar there’s a missing slash after the domain name. Instead of getting:

http://nagalokabuddhistcenter.org/2006/03/ I get
http://nagalokabuddhistcenter.org2006/03/

Any ideas what could be causing this? Any help much apprecaited.