Playing about and testing the code I have found that the default code puts out the following…
<a class="photolink" href="https://sphotos-b.ak.fbcdn.net/hphotos-ak-snc6/168702_164256273625794_5555704_n.jpg" rel="lightbox[galleryname]"><div class="photothumblarge" style="background-image: url(https://sphotos-b.ak.fbcdn.net/hphotos-ak-snc6/s320x320/168702_164256273625794_5555704_n.jpg)"></div></a>
<div class="photothumblarge" style="background-image: url(https://sphotos-b.ak.fbcdn.net/hphotos-ak-snc6/s320x320/168702_164256273625794_5555704_n.jpg)"></div>
Which does not fire the light box, but if you remove the last (repeated div photothumblarge it will work, any ideas how to stop it repeating this div?