Hi eduranti,
Welcome to the SEBLOD forums.
If you are using a WYSWYG editor field, you need to make sure that the the correct rights are granted and that it supports the public mode.
Also in the plugin Manager in the Admin Section , select type "cck_field" and find "CCK Field - Wysiwyg Editor". In it's configuration there is a setting to allow the wysiwyg for guest user.
You could also use a Textarea field type.
Hope that helps,
Randy