Hey,
to be honest I'm not sure why the plugins fetch the wrong image. You can try Slatelunchs open graph meta here: http://www.kriesi.at/support/topic/facebook-open-graph-protocol#post-23893
<!-- Facebook Opengraph -->
<meta property="fb:app_id" content="My Application ID" />
<meta property="fb:admins" content="My Admin ID" />
<?php if (is_single()) {
$preview_small = get_post_meta($post->ID, "_preview_small", true);
$preview_medium = get_post_meta($post->ID, "_preview_medium", true);
$preview_big = get_post_meta($post->ID, "_preview_big", true);
//defaults:
$preview = $preview_small;
$link_url = $preview_big;
$lightbox = 'boxes';
$link = true;
//change if necessary:
// resizing? => take next sized picture
if ($k_option['general']['tim'] == "1" && $preview_small == "")
{
$preview = $preview_medium != '' ? $preview_medium : $preview_big;
}
if (!kriesi_is_file($preview_big,'image'))
{
$preview = $preview_small != '' ? $preview_small : $preview_medium;
$link_url = $preview_big;
}
// no bigpicture? => no lightbox
if ($preview_big == "" || $k_option['portfolio']['portfolio_click'] == 2) { $lightbox = ''; $link = true; $link_url = get_permalink(); }
// the kriesi_build_image function used here checks if the image should be resized.
// the function is located in framework/helper_functions
$preview = kriesi_build_image(array('url'=>$preview,
'height'=> '124',
'width'=> '280',
'lightbox'=>$lightbox,
'link'=>$link,
'link_url'=>$link_url
));
?>
<meta property="og:url" content="<?php the_permalink() ?>"/>
<meta property="og:title" content="<?php single_post_title(''); ?>" />
<meta property="og:description" content="<?php the_excerpt_rss() ?>" />
<meta property="og:type" content="article" />
<meta property="og:image" content="<?php echo $preview; ?>" />
<?php } else { ?>
<meta property="og:site_name" content="My Website Name" />
<meta property="og:url" content="http://myurl.com"/>
<meta property="og:description" content="<?php bloginfo('description'); ?>" />
<meta property="og:type" content="website" />
<meta property="og:image" content="http://A default image url for the website.com" />
<?php } ?>
Adjust the admin id, etc. and add the meta tags before the body tag in header.php.