A thought (cos it happened to me years ago): you could be mixing SASL1 and SASL2 libraries. You don't state OS or vendor, but if it's Linux make sure you've included /usr/local/lib in /etc/ld.so.conf or one of the files in /etc/ld.so.conf.d (if you have it) and run ldconfig.
my system is freebsd 5.x
I am create file ld.so.conf with /usr/local/lib and I am run ldconfig
and slapd along crash after run ldapsearch -I and if I loged properly asl_interactive_bind_s: Can't contact LDAP server (-1)
and slapd show this:
==>slap_sasl2dn: converting SASL name uid=test,cn=example.com,cn=digest-md5,cn=auth to a DN slap_authz_regexp: converting SASL name uid=test,cn=example.com,cn=digest-md5,cn=auth <==slap_sasl2dn: Converted SASL name to <nothing> slapd in free(): error: chunk is already free Abort (core dumped)
but if I put bad password (when I login to slapd - digestmd5) - slapd along working..........
my installation dir for sasl2 is /usr/local/lib/sasl2 and with postfix is working correctly