Hmm, nope! Your input is definitely putting me on the right track, but it still looks like that call is still referencing the legacy WordPress thumbnail data. I'll do some digging of my own and try to see what's going on.
I did find this snippet that sheds a bit of light, but I'm still having unpredictable results with the thumbnail its returning. Sometimes it pulls the properly-sized image I'm looking for, sometimes it pulls the default 150x150.
<?php wp_get_attachment_image_src( get_post_thumbnail_id($post->ID), array( 60,60 ), false, '' ); ?>
Sorry for derailing by the way, but t31os_ you've been a huge help! Thanks!