I have an issue with installing KDE on my Ubuntu 14.04. I executed
apt-get install kubuntu-desktop
And tried to remove unity
sudo apt-get autoremove --purge unity unity-common unity-services
unity-lens-\* unity-scope-\* unity-webapps-\*
gnome-control-center-unity hud libunity-core-6\* libunity-misc4
libunity-webapps\* appmenu-gtk appmenu-gtk3 appmenu-qt\*
overlay-scrollbar\* activity-log-manager-control-center
firefox-globalmenu thunderbird-globalmenu libufe-xidgetter0
xul-ext-unity xul-ext-webaccounts webaccounts-extension-common
xul-ext-websites-integration gnome-control-center gnome-session
Next I chose KDM as default desktop manager. But now every time I logging in on KDM login screen all I see is empty default KDE wallpaper.
sudo apt-get install --reinstall kubuntu-desktop
Maybe you uninstalled something needed by KDE desktop.