This is an a common error in the blade and soul community that involves the games anti hacking software “Gameguard”
In order to solve this error you will need to navigate to your blade and soul game installation and delete the folder named “Gameguard”. Once it has been deleted you will need to restart your game and also for the game to download a new gameguard. Once the the game has finished downloading the program it should start up and work as normal.
Please note then when a new OS comes out for windows gameguard will take a few days and possibly weeks to be updated to work with the next version of the OS, doing the steps above will not solve your error if you are playing on a newly released operating system.