use the 4.0.1.1 download link, then rename the /webassist/ckeditor folder to ckeditor_back
copy the ckeditor folder from the download to the webassist folder to replace the old one.
from the ckeditor_back folder, copy the following three files:
ckeditor.php
ckeditor-php4.php
ckeditor-php5.php
and paste them in the new ckeditor folder.
you will need to clear the browsers cache to see the updates take effect.