dovecot - Mar 2014 - Problem with trying to use dsync with ldap userdb

Hello,

I'm trying to use dsync on a dovecot 2.2.12
I'm using an ldap database  as a user database with the following
configuration :

auth_bind = yes
ldap_version = 3
auth_bind_userdn = uid=%u,ou=People,dc=ipb,dc=fr
user_attrs = uidNumber=uid,gidNumber=gid

But I keet having the following errors : 

2014-03-14 17:53:37 doveadm(XXX): Debug: user XXX: Auth PASS lookup returned
temporary failure: reason=Configured passdbs don't support crentials lookups
2014-03-14 17:53:37 doveadm(XXX): Debug: auth input: reason=Configured passdbs
don't support crentials lookups
2014-03-14 17:53:37 doveadm(XXX): Error: sync:
/usr/local/var/run/dovecot/auth-userdb: Configured passdbs don't support
crentials lookups (to see if user is proxied, because doveadm_port is set)

I have been hunting through the doc for the last hours and I don't find what
to change.
I found something about adding 
set INSECURE_SETUID=1
export INSECUURE_SETUID
before checkpassword-reply launch, but it does not change anything...

 Btw my two server have use the users uid from the ldap, but don't allow
user login on the servers where only admin can log in.

Does somebody has an idea where to dig ?

f.g.