get_the_terms gives empty array

Hi, i keep getting an empty array when i use get_the_terms( $post->ID, 'actors').
On the other hand get_terms function gives me all ‘actors’! But I only want those actors which are related to a post. get_terms( 'actors', 'orderby=count&hide_empty=0' ); ?>
whats the trick?

http://ww.wp.xz.cn/extend/plugins/cpt-onomies/