[MikeF]

Alternative to save yourself some time:

showthread

Remove:

<vb:if condition="$show['fb_likebutton']">
            {vb:raw fblikebutton}
       </vb:if>

Replace:

<vb:if condition="$show['fb_likebutton']">
<table width="100%" border="0">
  <tr>
    <td>{vb:raw fblikebutton}</td>
    <td align="right"><g:plusone size="medium"></g:plusone></td>
  </tr>
</table>    
        </vb:if>

footer

Add to very end:

<script type="text/javascript" src="https://apis.google.com/js/plusone.js"></script>