Problem with multidomain and symbolic link - no input file specified

[eluser]Rwkzejedi[/eluser]
I have 1 dedicated server. The server has several IPs. Some IP are dedicated for one particular domain.

Ip1 = mysite.be
Ip2 = mysite.fr
Ip3 = mysite.com

There is only one project. Each domain goes on the same location

My website is on /var/www/vhosts/mysite.com/httpdocs

For all other domain, i create a symlink.

/var/www/vhosts/mysite.be/httpdocs -> /var/www/vhosts/mysite.com/httpdocs
/var/www/vhosts/mysite.fr/httpdocs -> /var/www/vhosts/mysite.com/httpdocs

...

When I go on mysite.com, all works. But when i go on mysite.be ... I have an output from codeIgniter :

No input file specified.

I search more information about this error and I see that : http://stackoverflow.com/a/14578219/905867

My .htaccess file is already well configured... I guess

Options +FollowSymLinks

RewriteEngine on
RewriteCond $1 !^(index\.php|robots\.txt|css|js|uploads|modules|public|timthumb\.php|\.htpasswd|google.*\.html|captcha)
RewriteRule ^(.*)$ /index.php?/$1 [L]

The fact that the domain linked with symlink display the error "No input file specified." proves that the symlink is OK and the acl on server are OK too (chown and chmod).

I think it's a little thing, but i don't know what. Anyone has a idea please ?