Auth with both mysql and imap

Hello,
I hope this is the right place to ask for a little help.

I'm trying to configure postfix to authenticate with both an SQL server and
an IMAP server.

My smtpd.conf:

pwcheck_method: auxprop saslauthd
mech_list: PLAIN LOGIN CRAM-MD5 DIGEST-MD5 NTLM

auxprop_plugin: sql
sql_engine: mysql
sql_hostnames: xxx
sql_user: xxx
sql_passwd: xxx
sql_database: xxx
sql_select: SELECT password FROM LoginUsers WHERE LoginUser = '%u@%r'


My /etc/default/saslauthd says:

MECHANISMS="rimap"
OPTIONS="-c -m /var/spool/postfix/var/run/saslauthd -r -O imap.server.com"


I'm able to do this things:
1) just auxprop works, if I telnet and make AUTH PLAIN with mysql user, OK
2) just saslauthd works, if I telnet and make AUTH PLAIN with imap user, OK
3) auxprop saslauthd with mysql user works, if I telnet and AUTH PLAIN with
mysql user OK
4) auxprop saslauthd with imap user DOESN'T WORK, if I telnet and AUTH
PLAIN with imap user FAILED

Strange thing is that with config 4 if I try testsaslauthd with the same
imap user it works.

I tried with both centos or debian, and it's the same. It doesn't seem a
permission problem.

Any hint on how to solve this?
On postfix forum are saying this seems a cyrus-sasl problem...

Thanks!!
Andrea