When hooking up OBIEE 11g to an LDAP, make sure to check some factors on the LDAP side of things as well. Not all errors have to come from your configuration in WLS:
First thing you should get is an LDAP browser with which to connect to the LDAP server to check validity of the connectivity ccount (i.e. the "Principal" for LDAP connectivity) as well as structures and object types. This will save you a lot of pain and suprising behaviour due to "ceative" LDAP management.