Post thumbnail not working after regenerate

Look at the wp-content/uploads/ directory. Does your cropped image exists there? (e.g. myimage-185x185.jpg). If not, you could try to call add_image_size() on the init action hook.

functions.php

function wpse27579_addImageSizes() {
    add_image_size('thumbnail-gallery', 185, 185, true);
}
add_action('init', 'wpse27579_addImageSizes');