Beg your pardon, wrong cut'n'paste.
Syslog says:
# less /var/log/syslog | grep dlz_bind9.so
May 26 22:33:44 doc named[22390]: dlz_dlopen: incorrect version 1 should be 2 in '/usr/lib/x86_64-linux-gnu/samba/bind9/dlz_bind9.so'
May 26 22:36:51 doc named[23846]: dlz_dlopen: incorrect version 1 should be 2 in '/usr/lib/x86_64-linux-gnu/samba/bind9/dlz_bind9.so'
May 26 22:37:01 doc named[23888]: dlz_dlopen: incorrect version 1 should be 2 in '/usr/lib/x86_64-linux-gnu/samba/bind9/dlz_bind9.so'
May 26 22:38:50 doc named[24163]: dlz_dlopen: incorrect version 1 should be 2 in '/usr/lib/x86_64-linux-gnu/samba/bind9/dlz_bind9.so'
May 26 22:39:28 doc named[24282]: dlz_dlopen: incorrect version 1 should be 2 in '/usr/lib/x86_64-linux-gnu/samba/bind9/dlz_bind9.so'
May 26 22:47:39 doc named[3295]: dlz_dlopen: incorrect version 1 should be 2 in '/usr/lib/x86_64-linux-gnu/samba/bind9/dlz_bind9.so'
May 26 22:49:30 doc named[7804]: dlz_dlopen: incorrect version 1 should be 2 in '/usr/lib/x86_64-linux-gnu/samba/bind9/dlz_bind9.so'
Samba is installed from wheezy-backports.
# apt-cache show samba
Package: samba
Version: 2:4.1.7+dfsg-2~bpo70+1
Installed-Size: 11014
Thank you.
I reverted back Bind9 (bind9, bind9utils, bind9-host, dnsutils) to versione 9.8 from Wheezy official repo and everything went ok.