Problem with some POST data

[eluser]Alhazred[/eluser]
In my application all the forms use the method POST, all of them works fine but one.

I have a link on a page, this link calls a controller's function, this function only loads a page.
Inside this page there is a form

Code:

<form id='moduserdata' name='moduserdata' method='post' action='<?php echo base_url().'users/mod_pers_data_act' ?>'>

I fill the form fields, press the submit button and it calls another method of the same controller above.
The problem is that if I try to print
echo $this->input->post('nome');
or any other field, nothing appears.

The form's action is correct because if I replace the echo above with
echo "blabla";
that appears.

The POST data look to don't arrive to the method, which could be the reason?