Validate plugin problem,

hello there.
I'm validate a form but sometimes does validate sometime no..

here is de link http://jsfiddle.net/darkporn/723Na/

the think is:
when I select any of the checkbox in the "incluir en el certificado" row. the form is validate as correct.
But I have to also validate "Subtipo" and "N° Copias"
Subtipo must be selected
and N° Copias must be at least 1, not numeric field

please help me.