Ad does not appear on Front Page (unauthenticated)

I have 3 image adds configured. They work correctly on all pages where the user is authenticated. On the main page, the add doesn't appear and firebug catches an error (firefox without firebug and IE do NOT report errors). WHen I look at the html for the page in firebug, there is a <script src="" type="text/javascript"> in the "block-ad-1" div with a huge piece of code that is html, not javascript. Here is a snippit:

<div class="sourceRow"><a class="sourceLine"> 1</a><span class="sourceRowText">&lt;!DOCTYPE html PUBLIC &quot;-//W3C//DTD XHTML 1.0 Strict//EN&quot;</span></div><div class="sourceRow"><a class="sourceLine"> 2</a><span class="sourceRowText"> &quot;http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd&quot;&gt;</span></div><div class="sourceRow"><a class="sourceLine"> 3</a><span class="sourceRowText">&lt;html xmlns=&quot;http://www.w3.org/1999/xhtml&quot; xml:lang=&quot;en&quot; lang=&quot;en&quot;&gt;</span></div><div class="sourceRow"><a class="sourceLine"> 4</a><span class="sourceRowText"> &lt;head&gt;</span></div><div class="sourceRow"><a class="sourceLine">

Strangely, if I view source in firefox or IE, all I get is:
<script type="text/javascript" src=""></script>

Either way, no ad.

Is this a configuration issue or a bug?

On the pages that display the ad correctly, I have:

<script type="text/javascript" src="http://thenazareths.com/ooa/modules/ad/adserve.php?g=default&c=none&p=files&f=3&q=1&k="></script>