This is posted in the Lion Server area — which is very old — and it's not entirely clear to me if this LDAP connection is attempting to connect from a client to an Open Directory LDAP directory running on a local Lion Server system, or if this is attempting to connect the directory to another directory server, or a client connecting to another directory server such as might be offered by local a Linux system. A few more details here might help me to be more certain of the configuration.
I'll assume that network connectivity has been verified, and that DNS is correctly configured for the server. If DNS for the server is hosed — name to address and address to name don't match up — then all sorts of problems can arise.
Check the LDAP server logs and see if there's anything relevant logged there.
FWIW, that domain.com domain is a real and registered domain, so I'm going to assume by your phrasing that isn't what you're using. For cases such as this as well as use in documentation and elsewhere, example.com, example.org and example.net are safer choices, as those domains are explicitly not real domains and will not be registered.