Indeed, as I suspected, you have to update the page http://wikifab.panglosslabs.org/wiki/Property:Difficulty?action=edit and copy the content from here : http://en.wikifab.org/index.php/Property:Difficulty?action=edit
And update the page http://wikifab.panglosslabs.org/wiki/Property:Duration-type?action=edit and copy content from http://en.wikifab.org/index.php?title=Property:Duration-type&action=edit
I hope there is no other page with this problem, it seems some french pages have been set instead of english version. I do not understand how. Have you changed wiki language at one moment during installation ?
An other way to correct would be to re-execute script "php maintenance/initWikifab.php" but this script must be edit first to force rewrite of existing page, by replacing this line (line 67) :
$this->createPage ( $title, $content );
by this one :
$this->createPage ( $title, $content, true );
or, If you create me an account I can help you to correct it (use my wikifab address: pierre at wikifab.org )