Ok.
Just found this on phpNuke 7.8 changes.txt:

Quote:

- Added a great WYSIWYG text editor to ALL PHP-Nuke's textarea fields. Compatible with Mozilla, MSIE and FireFox. For this was used the great tinyMCE made by MoxieCode Systems AB (http://tinymce.moxiecode.com). TinyMCE is free software released under the LGPL. All credits are untouched on the files (/includes/tinymce/). You don't need to do anything if you want your module to use the editor, it automaticaly replaces all and any <textarea> tags all over the place with the wysiwyg editor. This is what I call "easy of integration". Better configuration, implementation and cosmetic changes will come in future releases.

So... i guess i just have to find the css file where TEXTAREA tags are set.
Or not?!? :?

Maybe i can disable it somehow in some phpnuke var...

[EDIT]

Found in another line of changes.txt:

Quote:

- Added a new define('NO_EDITOR') method to remove the wysiwyg editor if you don't want it on a specific area use it as: define('NO_EDITOR', 1); just before including the header.php. On this way the wysiwyg editor will not load on that page

[EDIT II]

SOLVED!!

For anyone with the same problem, just get to modules/Private_Messages/index.php and add define('NO_EDITOR', 1); at the begining.