Hi,
Another detail I just noticed, I've an error on my contact form, that doesn't seems to relate to the visibility of my subject and message fields, but still...
Warning: Missing argument 1 for zpCaptcha::getCaptcha(), called in /XXX/XXX/XXX/plugins/contact_form/form.php on line 89 and defined in /XXX/XXX/XXX/zp-core/zp-extensions/zpCaptcha.php on line 144
So there seems to be a "miscommunication" between my form and the CMS...