If you decide to work with internal coded LdapContextSource initialize instead of using spring injection (external application context xml file). There is one important thing you shouldn't forget:
Call "afterPropertiesSet()" method to finish up initialization.
Failing to do so would probably led you to this failure / exception as i had:
"org.springframework.ldap.core.support.AbstractContextSource.getAuthenticatedEnv(AbstractContextSource.java:449) etc.."

Hopefully that this helps...
Dor