Please try a full clean re-install:
STEAM
- move any valued save games elsewhere
- "delete local files" in Steam
- manually delete all files left under Steam/CK2 AND Documents/CK2
- re-install game in Steam, run a verify when done.
GAMERSGATE
- move any valued save games elsewhere
- uninstall the game from Windows
- manually delete all files left under the GG CK2 AND Documents/CK2 folders
- re-install game from GG but point it to a new location outside the system path, such as c:\games\ck2\
- apply the latest patch (only)