Orderby = meta_value_num don´t work!

See my website:
http://www.susurrame.es/vibradores/

Clik in “Ordenar por: Precio | Valoracion | Opiniones”

Sortby comment_count is OK.

Sortby meta_value_num is WRONG

¿What happen?

Thanks.