just a comment: I am using v1.3.9d today and FCKeditor seems to be fine on the item editor but problem remains in the /admin/ezpages.php; I did a file comparison and found it was ok to replace this file with the 1.3.8a /admin/ezpages.php and this fixed the problem.

Maybe zencart have fixed the problem with FCKeditor in the latest version, I will see when I use it.