Update.. I deleted all CIFS shares, users and groups (added ones) and re-created everything and shares started to work... still I cannot understand what went wrong and why upload of saved configuration didn't help.
Update2 : Everything is saved and I tested to reboot freenas. Again files are not accessible and CIFS service won't restart. on console i can see :
an 26 22:49:45 freenas kernel: ada1: 300.000MB/s transfers (SATA 2.x, UDMA6, PIO 8192bytes)
Jan 26 22:49:45 freenas kernel: ada1: Command Queueing enabled
Jan 26 22:49:45 freenas kernel: ada1: 2861588MB (5860533168 512 byte sectors: 16H 63S/T 16383C)
Jan 26 22:49:45 freenas kernel: da0 at umass-sim0 bus 0 scbus8 target 0 lun 0
Jan 26 22:49:45 freenas kernel: da0: <Kingston DataTraveler G3 PMAP> Removable Direct Access SCSI-0 device
Jan 26 22:49:45 freenas kernel: da0: 40.000MB/s transfers
Jan 26 22:49:45 freenas kernel: da0: 3818MB (7819264 512 byte sectors: 255H 63S/T 486C)
Jan 26 22:49:45 freenas kernel: cd0 at ahcich7 bus 0 scbus7 target 0 lun 0
Jan 26 22:49:45 freenas kernel: cd0: <ATAPI DVD C DH48C2S NH36> Removable CD-ROM SCSI-0 device SMP: AP CPU #1 Launched!
Jan 26 22:49:45 freenas kernel: cd0: 150.000MB/s transfers
Jan 26 22:49:45 freenas kernel: (SATA 1.x, UDMA5, ATAPI 12bytes, PIO 8192bytes)
Jan 26 22:49:45 freenas kernel: cd0: Attempt to query device size failed: NOT READY, Medium not present
Jan 26 22:49:45 freenas kernel: GEOM: da0s1: geometry does not match label (16h,63s != 255h,63s).
Jan 26 22:49:45 freenas kernel: Trying to mount root from ufs:/dev/ufs/FreeNASs1a
Jan 26 22:49:45 freenas kernel: ZFS filesystem version 5
Jan 26 22:49:45 freenas kernel: ZFS storage pool version 28
Jan 26 22:49:45 freenas root: /etc/rc: WARNING: failed precmd routine for vmware_guestd
Jan 26 22:49:45 freenas ntpd[1606]: ntpd 4.2.4p5-a (1)
Jan 26 22:49:51 freenas avahi-daemon[1964]: WARNING: No NSS support for mDNS detected, consider installing nss-mdns!
Jan 26 22:49:55 freenas ntpd[1607]: time reset +0.797493 s
Jan 26 23:05:27 freenas ntpd[1607]: kernel time sync status change 2001
Jan 26 23:06:45 freenas notifier: Performing sanity check on Samba configuration: OK
Jan 26 23:06:45 freenas notifier: Reloading nmbd.
Jan 26 23:06:46 freenas notifier: Stopping dbus.
Jan 26 23:06:46 freenas notifier: Will not 'restart' dbus because dbus_enable is NO.
Jan 26 23:06:46 freenas notifier: Stopping avahi-daemon.
Jan 26 23:06:46 freenas avahi-daemon[1964]: Disconnected from D-Bus, exiting.
Jan 26 23:06:46 freenas notifier: Will not 'restart' avahi_daemon because avahi_daemon_enable is NO.
Jan 26 23:06:46 freenas notifier: smbd not running? (check /var/run/samba/smbd.pid).
Update3 : I took anonymous account away and re-created my shares with usernames and passwords. Now shares on CIFS still work after reboot.