I install Seven OES Server on a tree,and they work fine about a mouth.
But yesterday afternoon , Some Users could not login , and I check
messages that show some message below

Anyone know what reason that the issue occur.....

===================Messages =====================================
May 2 16:27:13 hqzdm1 /usr/sbin/namcd[7766]: Error [81] in LDAP search
while trying to find group FDNs with scope=base for cn=UNIX Workstation -
hqzdm1,ou=hq,o=mli
May 2 16:27:13 hqzdm1 /usr/sbin/namcd[7766]: Error [81] in LDAP search
while trying to find group FDNs with scope=base for cn=UNIX Workstation -
hqzdm1,ou=hq,o=mli
May 2 16:27:13 hqzdm1 /usr/sbin/namcd[7766]: Error [81] in LDAP search
for cn=admingroup,o=mli
May 2 16:27:13 hqzdm1 /usr/sbin/namcd[7766]: Error [81] in LDAP search
while trying to find group FDNs with scope=base for cn=UNIX Workstation -
hqzdm1,ou=hq,o=mli
May 2 16:27:13 hqzdm1 /usr/sbin/namcd[7766]: Error [81] in LDAP search
while trying to find group FDNs with scope=base for cn=UNIX Workstation -
hqzdm1,ou=hq,o=mli
May 2 16:27:14 hqzdm1 /usr/sbin/namcd[7766]: ldap_initconn: LDAP bind
failed, trying to connect to alternative LDAP server
May 2 16:27:14 hqzdm1 /usr/sbin/namcd[7766]: ldap_initconn: Unable to
bind to alternative LDAP servers either.
May 2 16:27:14 hqzdm1 /usr/sbin/namcd[7766]: Error [81] in LDAP search
while trying to find group FDNs with scope=base for cn=UNIX Workstation -
hqzdm1,ou=hq,o=mli
May 2 16:27:14 hqzdm1 /usr/sbin/namcd[7766]: write_errToSock: Write error
to socket, errno 32.
May 2 16:27:14 hqzdm1 /usr/sbin/namcd[7766]: ldap_initconn: LDAP bind
failed, trying to connect to alternative LDAP server
May 2 16:27:14 hqzdm1 /usr/sbin/namcd[7766]: ldap_initconn: Unable to
bind to alternative LDAP servers either.
May 2 16:27:14 hqzdm1 /usr/sbin/namcd[7766]: Error [81] in LDAP search
while trying to find group FDNs with scope=base for cn=UNIX Workstation -
hqzdm1,ou=hq,o=mli
May 2 16:27:14 hqzdm1 /usr/sbin/namcd[7766]: write_errToSock: Write error
to socket, errno 32.
May 2 16:27:14 hqzdm1 /usr/sbin/namcd[7766]: ldap_initconn: LDAP bind
failed, trying to connect to alternative LDAP server
May 2 16:27:14 hqzdm1 /usr/sbin/namcd[7766]: ldap_initconn: Unable to
bind to alternative LDAP servers either.
May 2 16:27:14 hqzdm1 /usr/sbin/namcd[7766]: Error [81] in LDAP search
while trying to find group FDNs with scope=base for cn=UNIX Workstation -
hqzdm1,ou=hq,o=mli
May 2 16:27:14 hqzdm1 /usr/sbin/namcd[7766]: write_errToSock: Write error
to socket, errno 32.
May 2 16:27:14 hqzdm1 /usr/sbin/namcd[7766]: ldap_initconn: LDAP bind
failed, trying to connect to alternative LDAP server
May 2 16:27:14 hqzdm1 /usr/sbin/namcd[7766]: ldap_initconn: Unable to
bind to alternative LDAP servers either.
May 2 16:27:14 hqzdm1 /usr/sbin/namcd[7766]: Error [81] in LDAP search
while trying to find group FDNs with scope=base for cn=UNIX Workstation -
hqzdm1,ou=hq,o=mli
May 2 16:27:14 hqzdm1 /usr/sbin/namcd[7766]: write_errToSock: Write error
to socket, errno 32.
May 2 16:27:14 hqzdm1 /usr/sbin/namcd[7766]: ldap_initconn: LDAP bind
failed, trying to connect to alternative LDAP server
May 2 16:27:14 hqzdm1 /usr/sbin/namcd[7766]: ldap_initconn: Unable to
bind to alternative LDAP servers either.
May 2 16:27:14 hqzdm1 /usr/sbin/namcd[7766]: Error [81] in LDAP search
while trying to find group FDNs with scope=base for cn=UNIX Workstation -
hqzdm1,ou=hq,o=mli
May 2 16:27:14 hqzdm1 /usr/sbin/namcd[7766]: write_errToSock: Write error
to socket, errno 32.
May 2 16:27:14 hqzdm1 /usr/sbin/namcd[7766]: ldap_initconn: LDAP bind
failed, trying to connect to alternative LDAP server
May 2 16:27:14 hqzdm1 /usr/sbin/namcd[7766]: ldap_initconn: Unable to
bind to alternative LDAP servers either.