Unfortunately, in the 4.5.x release series, it was possible for the password stored in LDAP for the admin user to be incorrect, as it was never actually used. This is because the admin user was also the LDAP rootdn user. 5.0 splits that out so that the rootdn user and the admin user are different. Unforutnately, this is exposing the fact that in some cases, the LDAP database password for the admin user was not set correctly in the past.
Sr. Member of Technical Staff
A Division of VMware, Inc.
Zimbra :: the leader in open source messaging and collaboration