open graph image being overwritten by gravatar logo?

Question

example page; http://www.c-art.org.uk/2011/07/01/jenny-abbot/

some reason the gravatar image is overwriting the posts featured image thumb (100x100). Nnot sure how its doing it! How can i get rid of it?

<meta property="og:title" content="Jenny Abbot" />
<meta property="og:description" content="C-Art — Cumbria Artist Open Studios, Jenny Abbot Artist Index PaintingC-Art"/>
<meta property="og:url" content="http://c-art.modernactivity.co.uk/?p=1254"/>
<meta property="og:image" content="http://www.c-art.org.uk/wp-content/uploads/Summer-at-Sea-Wood-100mm-100x100.jpg"/>
<meta property="og:type" content="article"/>
<meta property="og:site_name" content="C-Art"/>

best, dc.