Since you changed the image size to 200×300 you also need to modify the image size in functions.php:
add_image_size( 'teaser-thumb', 200, ( pinboard_get_option( 'crop_thumbnails' ) ? 300 : 9999 ), ( pinboard_get_option( 'crop_thumbnails' ) ? 1 : 0 ) );
Then you need to rebuild thumbnails with this plugin.