Hmm, can you try this instead:
Code:
<vb:if condition="$post['isfirstshown']">
<vb:if condition="$show['fb_likebutton']">
{vb:raw fblikebutton}
</vb:if>
</vb:if>
This will show on the first post of each page, but I'm sure we can figure out a way to ensure only page 1

I just want to make sure it's the conditional breaking, not anything else. So let me know if that works!
If it doesn't, we may need to register fblikebutton to postbit_legacy, in which case you're going to want the help of someone who understands hooks