Are you using any mods that might interfere with anything? Check also if you have an older version selected in the "BETAS" tab when you open properties. Should be "NONE" to select the current live patch.
If not, I recommend you to verify your files through Steam by going to your Steam library, Right click Crusader Kings II, choose properties, Local Files, and click "Verify Intergrity of Game Chache".
If that doesn't work. Try a complete re-install of the game. Don't forget to delete the CK2 folder at "Documents\Paradox Interactive\Crusader Kings 2" (Just make a backup of your save games first if you want to keep them!).
If not, I recommend you to verify your files through Steam by going to your Steam library, Right click Crusader Kings II, choose properties, Local Files, and click "Verify Intergrity of Game Chache".
If that doesn't work. Try a complete re-install of the game. Don't forget to delete the CK2 folder at "Documents\Paradox Interactive\Crusader Kings 2" (Just make a backup of your save games first if you want to keep them!).