This is the 2nd test, small change made to the img tag. changed
class="serendipity_image_link to
class="thickbox"
So, when you press on the image, the image should load on top of the page, with a gray overlay. If this doesn't happen, then all I can say is, it's not workin'. As the call for the script is very basic.
<a title="Clounds Over London" class="thickbox" href="/uploads/images/clouds_over_london.jpg"><img src=""/uploads/images/clouds_over_london.jpg"><img" width="110" vspace="5" hspace="5" height="83" border="0" style="border: 0px none ; padding-left: 5px; padding-right: 5px;" src="/uploads/images/clouds_over_london.serendipityThumb.jpg" alt="Clouds over London" /></a>
Fingers crossed this will work!?