Cannot boot normally, without restarting lightdm (or gdm)

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http://askubuntu.com – I had a problem precisely described here: http://www.webupd8.org/2013/01/ubuntu-lightdm-black-screen-when-using.html, black screen with blinking cursor instead of login screen. I've switched to gdm using sudo dpkg-reconfigure gdm -- but faced the same problem, now loading process stops on "red-white Ubuntu dots" (without activity under this splash). And to login, I still need to restart display manager: Ctrl+Alt+F1 and sudo service gdm restart. How to make Ubuntu to boot normally? (HowTos)