Firstly, thanks you answering me.
I confirm you that ldap server is running and working very well ("ps aux | grep ldap" confirm that).
I can make ldap-search, smbldap-**** commands, use phpldapadmin, ldap webmin fonctionnality.......
Apparently, ssh seems to be not involved in the problem.
I can't login localy too! and the log (auth.log) says :
(pam_unix) authentication failure; logname= uid=0 euid=0 tty=tty1 ruser= rhost= user=username
pam_ldap: ldap_simple_bind Can't contact LDAP server
FAILED LOGIN (1) on 'tty1' FOR `username', Authentication failure
The message is quite explicit. I really don't want to break my config by making bad manipulations...
So, again, please, help!!!