If it is broken and all you get is a list of images and instead of an image you get %POST_THUMB% try this...
Go into the plugin folder and open the file amtyThumb_posts.php.
On line 571 where it says:
echo "<br />" . $imgpath;
And take this, although it should already exist as a comment on line 573 and un-comment it or add it:
$temp = str_replace("%POST_THUMB%", $imgpath , $temp);
and that should do it.