Checked your site and it is a SEF problem or maybe a server configuration problem (maybe a problem in.htaccess) and not caused by uddeIM:
Wrong link:
http://www.***.com/acceder-a-la-messagerie-privee
A correct link without SEF:
http://www.***.com/index.php?option=com_uddeim
The correct link gives an error 500, so before(!) uddeIM is called the server is unable to evaluate the address.
Slabbi
uddeIM & uddePF Development
CB Language Workgroup
CB 3rd Party Developer