This will be a short post about that dammed Spell Checker that comes active by default in the Ckeditor module of Drupal. Well as to this day the best WYSIWYG Module in Drupal 6 (for me) is Ckeditor. Its simple to install, fast as hell at least compared to Fckeditor, and easy to configure, except the SpellChecker plugin.
By Default the SpellChecker plugin is active, and in english, so i couldnt find a way to deactivate it but at least I found the way to change the language. Just search for the string 'en_US' in the file ckeditor.js and change it according to the idiom you want.For spanish is 'es_ES'. You will found this file in the real ckeditor directory , not in the module.
That file is a minimized version of ckeditor. You can found the source in '_source' directory, just in case you wonder what does the real ckeditor do.