We got a zcs 5.0.18 working fine for some time but suddenly this afternoon the server stopped answering saying user/name passwords were incorrect.

I did a zmcontrol status and got this error:
Unable to determine enabled services from ldap.
Enabled services read from cache. Service list may be inaccurate.
Checked the forum and verified the hosts file, dns records, certificate... and everything seems correct.

Here is a few lines of the zimbra.log file:

Code:
Sep 19 22:00:45 mail2 slapd[1872]: conn=496 op=0 STARTTLS 
Sep 19 22:00:45 mail2 slapd[1872]: conn=496 op=0 RESULT oid= err=0 text= 
Sep 19 22:00:45 mail2 slapd[1872]: conn=496 fd=23 TLS established tls_ssf=128 ssf=128 
Sep 19 22:00:45 mail2 slapd[1872]: conn=496 op=1 BIND dn="uid=zimbra,cn=admins,cn=zimbra" method=128 
Sep 19 22:00:45 mail2 slapd[1872]: conn=496 op=1 BIND dn="uid=zimbra,cn=admins,cn=zimbra" mech=SIMPLE ssf=0 
Sep 19 22:00:45 mail2 slapd[1872]: conn=496 op=1 RESULT tag=97 err=0 text= 
Sep 19 22:00:45 mail2 slapd[1872]: conn=496 op=2 SRCH base="cn=servers,cn=zimbra" scope=2 deref=3 filter="(objectClass=zimbraServer)" 
Sep 19 22:00:45 mail2 slapd[1872]: conn=496 op=2 SEARCH RESULT tag=101 err=0 nentries=1 text= 
Sep 19 22:00:45 mail2 slapd[1872]: conn=497 fd=24 ACCEPT from IP=192.168.0.16:51924 (IP=192.168.0.16:389) 
Sep 19 22:00:45 mail2 slapd[1872]: conn=497 op=0 STARTTLS 
Sep 19 22:00:45 mail2 slapd[1872]: conn=497 op=0 RESULT oid= err=0 text= 
Sep 19 22:00:45 mail2 slapd[1872]: conn=497 fd=24 TLS established tls_ssf=128 ssf=128 
Sep 19 22:00:45 mail2 slapd[1872]: conn=497 op=1 BIND dn="uid=zimbra,cn=admins,cn=zimbra" method=128 
Sep 19 22:00:45 mail2 slapd[1872]: conn=497 op=1 BIND dn="uid=zimbra,cn=admins,cn=zimbra" mech=SIMPLE ssf=0 
Sep 19 22:00:45 mail2 slapd[1872]: conn=497 op=1 RESULT tag=97 err=0 text= 
Sep 19 22:00:45 mail2 slapd[1872]: conn=497 op=2 SRCH base="cn=config,cn=zimbra" scope=0 deref=3 filter="(objectClass=*)" 
Sep 19 22:00:45 mail2 slapd[1872]: conn=497 op=2 SEARCH RESULT tag=101 err=0 nentries=1 text= 
Sep 19 22:00:46 mail2 slapd[1872]: conn=497 fd=24 closed (connection lost) 
Sep 19 22:00:46 mail2 slapd[1872]: conn=496 fd=23 closed (connection lost) 
Sep 19 22:00:47 mail2 slapd[1872]: conn=498 fd=23 ACCEPT from IP=192.168.0.16:51925 (IP=192.168.0.16:389) 
Sep 19 22:00:47 mail2 slapd[1872]: conn=498 op=0 STARTTLS 
Sep 19 22:00:47 mail2 slapd[1872]: conn=498 op=0 RESULT oid= err=0 text= 
Sep 19 22:00:47 mail2 slapd[1872]: conn=498 fd=23 TLS established tls_ssf=128 ssf=128 
Sep 19 22:00:47 mail2 slapd[1872]: conn=498 op=1 BIND dn="uid=zimbra,cn=admins,cn=zimbra" method=128 
Sep 19 22:00:47 mail2 slapd[1872]: conn=498 op=1 BIND dn="uid=zimbra,cn=admins,cn=zimbra" mech=SIMPLE ssf=0 
Sep 19 22:00:47 mail2 slapd[1872]: conn=498 op=1 RESULT tag=97 err=0 text= 
Sep 19 22:00:47 mail2 slapd[1872]: conn=498 op=2 SRCH base="cn=servers,cn=zimbra" scope=2 deref=3 filter="(&(objectClass=zimbraServer)(zimbraServiceEnabled=imapproxy))" 
Sep 19 22:00:47 mail2 slapd[1872]: conn=498 op=2 SEARCH RESULT tag=101 err=0 nentries=1 text= 
Sep 19 22:00:47 mail2 slapd[1872]: conn=499 fd=24 ACCEPT from IP=192.168.0.16:51926 (IP=192.168.0.16:389) 
Sep 19 22:00:47 mail2 slapd[1872]: conn=499 op=0 STARTTLS 
Sep 19 22:00:47 mail2 slapd[1872]: conn=499 op=0 RESULT oid= err=0 text= 
Sep 19 22:00:47 mail2 slapd[1872]: conn=499 fd=24 TLS established tls_ssf=128 ssf=128 
Sep 19 22:00:47 mail2 slapd[1872]: conn=499 op=1 BIND dn="uid=zimbra,cn=admins,cn=zimbra" method=128 
Sep 19 22:00:47 mail2 slapd[1872]: conn=499 op=1 BIND dn="uid=zimbra,cn=admins,cn=zimbra" mech=SIMPLE ssf=0 
Sep 19 22:00:47 mail2 slapd[1872]: conn=499 op=1 RESULT tag=97 err=0 text= 
Sep 19 22:00:47 mail2 slapd[1872]: conn=499 op=2 SRCH base="cn=config,cn=zimbra" scope=0 deref=3 filter="(objectClass=*)" 
Sep 19 22:00:47 mail2 slapd[1872]: conn=499 op=2 SEARCH RESULT tag=101 err=0 nentries=1 text= 
Sep 19 22:00:48 mail2 slapd[1872]: conn=499 fd=24 closed (connection lost) 
Sep 19 22:00:48 mail2 slapd[1872]: conn=498 fd=23 closed (connection lost) 
Sep 19 22:00:49 mail2 slapd[1872]: conn=500 fd=23 ACCEPT from IP=192.168.0.16:51927 (IP=192.168.0.16:389) 
Sep 19 22:00:49 mail2 slapd[1872]: conn=500 op=0 STARTTLS 
Sep 19 22:00:49 mail2 slapd[1872]: conn=500 op=0 RESULT oid= err=0 text= 
Sep 19 22:00:49 mail2 slapd[1872]: conn=500 fd=23 TLS established tls_ssf=128 ssf=128 
Sep 19 22:00:49 mail2 slapd[1872]: conn=500 op=1 BIND dn="uid=zimbra,cn=admins,cn=zimbra" method=128 
Sep 19 22:00:49 mail2 slapd[1872]: conn=500 op=1 BIND dn="uid=zimbra,cn=admins,cn=zimbra" mech=SIMPLE ssf=0 
Sep 19 22:00:49 mail2 slapd[1872]: conn=500 op=1 RESULT tag=97 err=0 text= 
Sep 19 22:00:49 mail2 slapd[1872]: conn=500 op=2 SRCH base="cn=servers,cn=zimbra" scope=2 deref=3 filter="(objectClass=zimbraServer)" 
Sep 19 22:00:49 mail2 slapd[1872]: conn=500 op=2 SEARCH RESULT tag=101 err=0 nentries=1 text= 
Sep 19 22:00:49 mail2 slapd[1872]: conn=501 fd=24 ACCEPT from IP=192.168.0.16:51928 (IP=192.168.0.16:389)
Can anyone point me a clue of what can be happening ?