Comment 1 for bug 506317

Here's the workaround. The bug is caused because the migration seems to forbid anonymous access to subschema which is required by tools like phpldapadmin and urlfetch.

1) Stop your ldap server.

2) modify the slapd.conf file to add the following :

access to dn="cn=subschema"
   by * read

# before the first database definition
database config
# NOTE: the suffix is hardcoded as cn=config and
# MUST not have a suffix directive
# normal rules apply - rootdn can be anything you want
# but MUST be under cn=config
rootdn "cn=admin,cn=config"
# use any of the supported password formats e.g. {SSHA} etc
# or plaintext as shown
rootpw config

3) remove the slapd.d folder (but keep a backup)

4) generate a new slapd.d folder :
slaptest -f slapd.conf -F slapd.d

5) change its ownership :
chown -R openldap:openldap slapd.d

6) restart slapd ! It works !

Useful related links :
http://phpldapadmin.sourceforge.net/wiki/index.php/FAQ#I_cannot_view_the_schema.2C_or_I_get_the_message_.22Our_attempts_to_find_your_SCHEMA_for_.27objectclasses.27_have_FAILED..22
http://www.zytrax.com/books/ldap/ch6/slapd-config.html