murder authentication frontend -> backend problem

[cyrus @ Sylconia]

Hello,

currently i am setting up a loadbalanced frontend -> backend cyrus imap 
solution (murder).
Currently we are running 2 frontends (1 mupdate master on frontend) en 1 
backend server.

software  Cyrus POP3 Murder v2.2.12-Invoca-RPM-2.2.12-8.1.RHEL4  on 
Centos 4.4

backend imapd.conf:
configdirectory: /var/lib/imap
partition-default: /var/spool/imap
admins: cyrus
sievedir: /var/lib/imap/sieve
sendmail: /usr/sbin/sendmail
hashimapspool: true
sasl_pwcheck_method: saslauthd
sasl_mech_list: PLAIN
allowplaintext: yes
virtdomains: userid
defaultdomain: localhost.localdomain
unixhierarchysep: yes
allowusermoves: yes
tls_cert_file: /usr/share/ssl/certs/cyrus-imapd.pem
tls_key_file: /usr/share/ssl/certs/cyrus-imapd.pem
tls_ca_file: /usr/share/ssl/certs/ca-bundle.crt
tls_require_cert: 0
mupdate_server: server01
mupdate_port: 3905
mupdate_authname: cyrus
mupdate_username: cyrus
mupdate_password: cyrus
proxyservers: murder

frontend imapd.conf:
configdirectory: /var/lib/imap
partition-default: /var/spool/imap
admins: cyrus
sasl_pwcheck_method: saslauthd
sasl_mech_list: PLAIN
sasl_minimum_layer: 0
allowplaintext: yes
virtdomains: userid
defaultdomain: localhost.localdomain
unixhierarchysep: yes
allowusermoves: yes
tls_cert_file: /usr/share/ssl/certs/cyrus-imapd.pem
tls_key_file: /usr/share/ssl/certs/cyrus-imapd.pem
tls_ca_file: /usr/share/ssl/certs/ca-bundle.crt
mupdate_server: server01
mupdate_port: 3905
mupdate_authname: cyrus
mupdate_username: cyrus
mupdate_password: cyrus
# How to get to backends
server05_sylconia_nl_authname: murder
server05_sylconia_nl_password: murder
proxy_authname: murder

I am using LDAP to authenticate users which is working fine. When i 
login with Thunderbird for example to the backend their is nog problem 
but when i try to login via the frontend. I receive the following error

Jun 12 16:31:46 server02 imap[7181]: login: [192.168.1.100] 
email at domain.nl plaintext
Jun 12 16:31:46 server02 imap[7181]: Doing a peer verify
Jun 12 16:31:46 server02 imap[7181]: verify error:num=18:self signed 
certificate
Jun 12 16:31:46 server02 imap[7181]: received server certificate
Jun 12 16:31:46 server02 imap[7181]: starttls: TLSv1 with cipher 
AES256-SHA (256/256 bits new) no authentication
Jun 12 16:31:46 server02 imap[7181]: couldn't authenticate to backend 
server: no mechanism available

any suggestions or tips?

Regards
Constan