[Samba] Can't login to Windows 2012R2 with domain user

[Bogdan Rudas]

Hello!

This is my first Samba experience. Pre-condition:
1. Ubuntu 14.04 with updates installed
2. Samba 4.2.2 from Sernet repo
3. Pure Windows 2012 R2 server

Both Linux and Windows are fresh systems, no antivirus on Windows, no
firewall on Linux.
AD was provisioned by https://wiki.samba.org/index.php/Samba_AD_DC_HOWTO
manual.
sernet-samba-ad package installed, SAMBA_START_MODE="ad" in
/etc/default/sernet-samba
All test from manual was performed.

Symptoms: Windows was joined to domain, and after reboot login attempt was
performed via KVM. Login as AD admininstrator was successful. Then I try to
login via RDP with same credentials, Windows stuck on "Welcome" screen -
see http://gyazo.com/12f7a7274445ee7c0eec8bd7b29cf20d and I can't even
login via KVM console until power cycle.

Please, help me investigate this issue.

Thank you.