Making some progress.. The following will help :
here is the answer from the hosting company :
"
This lead me from doku.php to inc/init.php to inc/load.php where it fails at the line:
// setup class autoloader
spl_autoload_register('load_autoload');
I don't know PHP very well but I am pretty sure that to use that call PHP needs to be built with SPL support. Our PHP isn't built with support for this extension/module due to a problem compiling PHP with support for it. Since you are already running a copy of DokuWiki I assume that it must be an older version which does not need SPL support. This seems to be why the program isn't running though."
I installed the "lemming version (2009-12-25c)" to see if the problem was recurrent with that hosting company and voila!
http://www.citoyensbh.com/dokuwiki99/doku.php (This is a test installation of the Lemming version)
It seems to run fine.... or at least I am not getting a "blank page" on the first run...
So what happened between the two version (lemming that works) and (Anteater that does not work) that seems to create a problem???
Any idea?