Query works in LDAP v2 but not in LDAP v3

[Hubertus von Fürstenberg <hubertus@ise.fhg.de>]

Whilst upgrading to from LDAP v2 (openldap-2.0.19) to LDAP v3 
(openldap-2.1.30) I have encountered the following problem:

The query
ldapsearch -x 'uniqueMember=uid=hubertus*'
returned a result on the old version:

version: 2

#
# filter: uniqueMember=uid=hubertus*
# requesting: ALL
#

# sc-unix, Groups, ISE, Fraunhofer
dn: cn=sc-unix,ou=Groups,ou=ISE, o=Fraunhofer
objectClass: top
objectClass: groupOfUniqueNames
cn:: c2MtdW5peCA=
uniqueMember: uid=hubertus,ou=People,ou=ISE,o=Fraunhofer
uniqueMember: uid=peja,ou=People,ou=ISE,o=Fraunhofer

# netadmin, Groups, ISE, Fraunhofer
dn: cn=netadmin,ou=Groups,ou=ISE, o=Fraunhofer
objectClass: top
objectClass: groupOfUniqueNames
cn: netadmin
uniqueMember: uid=hubertus,ou=People,ou=ISE,o=Fraunhofer
uniqueMember: uid=peja,ou=People,ou=ISE,o=Fraunhofer
<snip>
# search result
search: 2
result: 0 Success

# numResponses: 11
# numEntries: 10


but the same query brought no results on the LDAP v3

# LDAPv3
# base <> with scope sub
# filter: uniqueMember=uid=hubertus*
# requesting: ALL
#

# search result
search: 2
result: 0 Success

# numResponses: 1


A query for the DN of the group shows, that the data is there


ldapsearch -x 'cn=sc-unix'
# extended LDIF
#
# LDAPv3
# base <> with scope sub
# filter: cn=sc-unix
# requesting: ALL
#

# sc-unix, Groups, ISE, Fraunhofer
dn: cn=sc-unix,ou=Groups,ou=ISE,o=Fraunhofer
objectClass: top
objectClass: groupOfUniqueNames
cn:: c2MtdW5peCA=
uniqueMember: uid=hubertus,ou=People,ou=ISE,o=Fraunhofer
uniqueMember: uid=peja,ou=People,ou=ISE,o=Fraunhofer


Can anybody tell me, what went wrong?

Thanks,
Hubertus

--
Hubertus von Fuerstenberg
 Fraunhofer Institut                 Telefon   +49 761 4588 -5 327
 Solare Energiesysteme       Telefax   +49 761 4588 -9 286
 Heidenhofstrasse 2            
 D-79110 Freiburg                 email: hubertus@ise.fraunhofer.de