I have a hunch on what might be going wrong.
1. Backup and delete the contents of Documents\Paradox Interactive\Crusader Kings II\gfx\flags
2. Relaunch the game and see if it works now.
3. If it doesn't, empty that directory again and then disable your Antivirus software (or whitelist CK2) before launching the game again.
1. Backup and delete the contents of Documents\Paradox Interactive\Crusader Kings II\gfx\flags
2. Relaunch the game and see if it works now.
3. If it doesn't, empty that directory again and then disable your Antivirus software (or whitelist CK2) before launching the game again.