Okay, I’m going on the assumption that the real question is “how do I get Thematic to add the post-format to its body classes?”
Try this in your functions.php:
function my_thematic_post_format_class( $classes = array() ) {
$format = get_post_format();
if ( '' == $format )
$format="standard";
$classes[] = 'format-' . $format;
return $classes;
}
add_filter( 'post_class', 'my_thematic_post_format_class' );
Don’t override the thematic post class functions. Just add that filter, and you should be good.