Author have to use WP_PLUGIN_DIR constant for the plugin path:
function wp_cycle_scripts() {
if(!is_admin())
wp_enqueue_script('cycle', WP_CONTENT_URL.'/plugins/wp-cycle/jquery.cycle.all.min.js', array('jquery'), '', true);
}
should sound like
function wp_cycle_scripts() {
if(!is_admin())
wp_enqueue_script('cycle', WP_PLUGIN_DIR.'/wp-cycle/jquery.cycle.all.min.js', array('jquery'), '', true);
}