Make sure that the hostname in the certificate and the hostname you use in the ldap settings are identical. So if your host is
dc1.mydomain.com and your connecting to 192.168.1.7, Java will complain. You may then correct the URL, possibly add the hostname and IP address to your hosts file or use the promiscuous mode. The latter, however, is not recommended in production and especially not if traffic is passing open and untrusted networks.
If all the above are correct, check connectivity and check whether the correct certificate is presented, using openssl command line tools:
$ openssl s_client -connect host.domain:636 -showcerts
Regards,
Menno Pieters