Many thanks for your answer,
I've made the process as your request, the system answer is :

root@ks215224:/var/www/vhosts/parti-radical-var.fr/httpdocs/multisites/test# ls -lA
total 32
drwxr-xr-x 2 pr-var psacln 4096 2012-08-24 20:41 cache
-rw-r--r-- 1 pr-var psacln 559 2012-08-24 20:41 config_multisites.php
-rw-r--r-- 1 pr-var psacln 494 2012-08-24 20:41 index2.php
-rw-r--r-- 1 pr-var psacln 492 2012-08-24 20:41 index.php
drwxr-xr-x 10 pr-var psacln 4096 2012-08-24 20:41 installation
drwxr-xr-x 2 pr-var psacln 4096 2012-08-24 20:41 logs
drwxr-xr-x 7 pr-var psacln 4096 2012-08-24 20:41 templates
drwxr-xr-x 2 pr-var psacln 4096 2012-08-24 20:41 tmp

Hope it helps !

This clearly shows that you didn't deployed the symbolic link in the "test" directory and also that there is no physical directory exists.

Verify the "deploy folder" path and also verify that your server accept to deploy the symbolic links. You can go in the "settings" menu to see if Symbolic Link is allowed.

Verify also the permission of the test directory. Perhaps that you should be increased the permission with 777.

The error that you have with the "symbolic link" creation let me suppose this is a permission error. Perhaps this is due to the ownership of the directory.