"You need to be registered member to access this area"
This option is forbidden by webmaster's decision."

In data/config.inc :

Check

A)- line 131

$serviz[28] = stripslashes("on"); // visitors preferences


B)- line 145 :

$serviz[42] = stripslashes(""); // Writer  Option ON / OFF

Il ne doit pas y avoir de "on" ; s'il y est, le supprimer.

Try to display the page by presing CTRL + F5, and even empty the cache  (temporary Internet files)

Nota: Administrator has to register as a member.
1 - When collaborators (writer, moderator,...) are wanted.
2 - To put the website into maintenance... Enfin surtout pour le sortir de la maintenance.
You'd then better register as explained in the Manual, so that all problems will be avoided.