Please try a full clean reinstallation
Important: Go to '..\Documents\Paradox Interactive\Crusader Kings II\save games\' and copy all the save games you want to keep outside the folder
* Uninstall Crusader Kings II.
* Steam users: uninstall the game from within steam by right clicking on the game and select "Delete content"
* Go to the folder where you installed Crusader Kings II in, and check if the Crusader Kings II folder is removed. If not, delete the entire folder
* Steam users: Installation folder can be found at: '..\Steam\SteamApps\common\'
* Go to '..\My Documents\Paradox Interactive\' and remove the entire Crusader Kings II folder
* Re-install the game - Make sure to install the game outside the 'C:\Program Files\' or 'C:\Program Files (x86)\' folders, as it can cause issues with permissions