Hi People, 
Iḿ using 14.04 and experienced this bug on first try to switch users.

FRESH install of 14.04.
My user as computer admin, my wife as normal user, another 3 users (nerver logged in) 

steps: 
1. Boot
2 . Logged in with first user
3. Upper rigth "gear" icon -> sithch user
4. Desktop shows screen with all users, but frezzes completely

-> not able to ctrl-alt-Fn to any tty
-> If previosly openned a TTY not able to switch back

The only UI custom sets where enable local menus , language settings portuguese,, enable  directory sort on nautilus and set wallpaper.


===== SETUP PACKAGES ==========
After fresh install:
sudo apt-get update && sudo apt-get upgrade
sudo apt-get install geany  geany-plugins vim zim nmon
--
sudo apt-get install gimp gimp-data gimp-data-extras gimp-plugin-registry  graphviz gnuplot feedgnuplot gnuplot-doc libgnuplot-iostream-dev python-gnuplot graphviz-doc  icu-doc 
fontforge fontforge-extras icontool imagemagick inkscape
sudo apt-get install vlc zim  unity-tweak-tool mplayer smplayer 
sudoo apt-get install gstreamer0.10-plugins-ugly libxine1-ffmpeg gxine mencoder libdvdread4 totem-mozilla icedax tagtool easytag id3tool lame nautilus-script-audio-convert libmad0 mpg321 libavcodec-extra
l ubuntu-restricted-extras   
sudo /usr/share/doc/libdvdread4/install-css.sh
----
sudo apt-get install clamav clamtk
--
#### Java
sudo apt-get install openjdk-7-jdk openjdk-7-jre icedtea-7-plugin
sudo add-apt-repository ppa:webupd8team/java
sudo apt-get update
sudo apt-get install oracle-java8-installer
sudo apt-get install oracle-java7-installer
sudo apt-get install oracle-java6-installer
---
sudo apt-get install skype
sudo apt-get install filezilla filezilla-common
sudo apt-get install unace rar unrar p7zip-rar p7zip zip unzip sharutils uudeview mpack arj cabextract file-roller
---
sudo apt-get install darktable digikam

#### Chrome
wget -q -O - https://dl-ssl.google.com/linux/linux_signing_key.pub | sudo apt-key add -
sudo sh -c 'echo "deb http://dl.google.com/linux/chrome/deb/ stable main" >> /etc/apt/sources.list.d/google.list'
sudo apt-get update
sudo apt-get install google-chrome-stable
----
sudo apt-get install activity-log-manager activity-log-manager-control-center
sudo apt-get install gufw
--
#### NETFLIX
sudo apt-add-repository ppa:ehoover/compholio;
sudo apt-get update ;
sudo apt-get install netflix-desktop redbox-desktop lovefilm-desktop;
--
#### Virtualbox
sudo sh -c 'echo "deb http://download.virtualbox.org/virtualbox/debian $(lsb_release -sc)  contrib" >> /etc/apt/sources.list'
sudo sh -c 'echo "deb http://download.virtualbox.org/virtualbox/debian $(lsb_release -sc)  contrib" >> /etc/apt/sources.list'
wget -q http://download.virtualbox.org/virtualbox/debian/oracle_vbox.asc -O- | sudo apt-key add -
sudo apt-get update & sudo apt-get install virtualbox
---
sudo apt-get install flashplugin-installer
sudo apt-get install nmon
sudo apt-get install unity-tweak-tool
sudo apt-get install gnome-tweak-tool
--
#### Dropbox
sudo apt-get install nautilus-dropbox
sudo apt-get install libappindicator1
---
#### Pipelight
sudo apt-add-repository ppa:pipelight/stable
sudo apt-get update
sudo apt-get install pipelight-multi
sudo pipelight-plugin --enable silverlight
sudo pipelight-plugin --enable widevine
----
sudo add-apt-repository ppa:linrunner/tlp
sudo apt-get update
sudo apt-get install tlp tlp-rdw
sudo tlp start
---
Setting Nautilus preferences...'
    gsettings set org.gnome.nautilus.preferences sort-directories-first true
--
sudo apt-get install svn git bzr nodejs python3-distutils-extra glade 
sudo apt-get install openssh-server
--
sudo apt-get install mysql-server
sudo apt-get install libqt4-sql-mysql

=== Istall Brasil IRS Anual Report java software.

sudo apt-get -f install 
sudo apt-get autoremove 
sudo apt-get -y autoclean 
sudo apt-get -y clean
================ INSTALL STEPS =======

After this I setup digikam with mysql  and HP PSC-1510C printer.

Except java app, hplip nmon, digikam, mysql, zim, zip chrome, firefox and libreoffice I not used any of the other softwares installerd , yet.

On Software & Updates -> Additional drivers -> nothing was change since install
No pproprietary drivers in use
Using X.Org Server - Noveau display driver from xserver-xorg-video-noveau.

Please guide me how to select/extract any other logs that might help.