img tags appearing on rendered page

This screenshot describes what I mean: http://screencast.com/t/ZTdlNDRkZTMt

The img tags are being filtered somewhere (I'm not using an input filter so it must be soomewhere else) and I end up with this in the html for the page:

    <ul class="links inline">
      <li class="first service_links_delicious">
        <a href="http://del.icio.us/post">&lt;img
        src="/sites/fhfvp.illuminateweb.org.uk/modules/service_links/images/delicious.png"
        alt="del.icio.us" title="" width="16" height="16" /&gt;</a>
      </li>
      <li class="service_links_digg">
        <a href="http://digg.com/submit">&lt;img
        src="/sites/fhfvp.illuminateweb.org.uk/modules/service_links/images/digg.png"
        alt="Digg" title="" width="16" height="16" /&gt;</a>
      </li>
      <li class="service_links_facebook">
        <a href="http://www.facebook.com/sharer.php">&lt;img
        src="/sites/fhfvp.illuminateweb.org.uk/modules/service_links/images/facebook.png"
        alt="Facebook" title="" width="16" height="16" /&gt;</a>
      </li>
      <li class="last service_links_twitter">
        <a href="http://twitter.com/home/">&lt;img
        src="/sites/fhfvp.illuminateweb.org.uk/modules/service_links/images/twitter.png"
        alt="Twitter" title="" width="16" height="16" /&gt;</a>
      </li>
    </ul>

Any ideas why this is happening? I've used service links before without this problem.

Many thanks.