Wordpress : URL error 404 but the page exists

[admin]

I moved my wordpress (3.0) blog to my dedicaced server.

Just one thing is broken :

if i set the url in worpress to be

http://wwww.example.com/page?id=3

<strong>The page is correctly shown</strong>

If i set the URL to be :

http://wwww.example.com/about/
http://www.example.com/services/

<strong>it ends up with a 404 not found page !!</strong>

Here's my virtual host if it helps :

<VirtualHost *:80>
   ServerAdmin webmaster@localhost
   ServerName www.example.fr

    DocumentRoot /var/www/example
    <Directory /var/www/example>
            Options -Indexes FollowSymLinks MultiViews
            AllowOverride None
            Order allow,deny
            allow from all
    </Directory>


    # Possible values include: debug, info, notice, warn, error, crit,
    # alert, emerg.
    LogLevel warn

    CustomLog /var/log/apache2/access-example.log combined
    ErrorLog /var/log/apache2/error-example.log
    ServerSignature Off
</VirtualHost>

Thanks you