Logged in as admin spellcheck works fine. But if another user on same PC logs in, Atlantis runs but spellcheck doesn't. My guess is it has to do with privileges, but not certain....
Every user has its personal settings of Atlantis in the Windows Registry. Every user can "install" (specify) the desired spellcheckers through the "Spellcheck" page of the "Tools | Options" dialog of Atlantis.
