I did some research, and it seems like I should have noticed this last time ... The server is still adding some javascripts to all the pages, something that corrupts the Imagevue PHP files.
You can see in the INDEX page -
http://www.nicolashodee.fr/upload/ - View source, and you will see the following line added at the top:
<script language="JavaScript" type="text/javascript" src="/xdir-frame-publicite.js"></script>
... and at the bottom:
<script language="JavaScript" type="text/javascript">try{parent.document.title=document.title;}catch(error){}</script><script language="JavaScript" type="text/javascript">try{var referer=top.document.referrer;}catch(error){var referer=document.referrer;};var source='/xdir-statistiques.js?referer='+escape(referer)+'&'+new String(Math.random()).substring(2,11);document.write('<scr'+'ipt language="JavaScript" type="text/javascript" src="'+source+'"></scr'+'ipt>');</script>
This does not actually do any damage to the main index page, but it does do damage to all the Imagevue scripts, like
http://www.nicolashodee.fr/upload/dir.php
Perhaps you can send an email to your host and ask them what it is, and if they can remove it? You should certainly be able to demand such if it is a paid service.