I think the FormDhtmlExt editor was part of the xoopseditors package from years ago. I think your site might have the files on your site still (I don't know if there in an updated version available). Go to the system module->preferences->system module settings. In the 'Editor Settings' , change all of the editors to 'dhtmltextarea'. Now your site will use an editor that works.
The preference page should be here:
Quote:
htdocs/modules/system/admin.php?fct=preferences&op=showmod&mod=1