File field and AHAH button not working together in dynamic form

I faced some problem with file filed and AHAH button both together. But File field and AHAH button not working together.
For some reason, file uploads don't like drupal_json() with its manual setting of the text/javascript HTTP header. So use this one instead.

Solution:
==========
Instead of using
"drupal_json(array('status' => TRUE, 'data' => $output));"
need to use
" print drupal_to_js ( array ( 'status' => TRUE, 'data' => $output ) ); exit "