Firstly, make sure that your computer meets the minimum system requirements to run the game:
- OS: Windows 2000 Service Pack 4 or Windows XP;
- CPU: Pentium 4 with 1.4 GHz or higher;
- RAM: 512 MB or higher;
- Video Card: Geforce FX, Radeon 9600 or higher;
- Video Card RAM: 128 MB or higher;
- DirectX: 9.0c or higher;
- HDD Space: 6GB or higher.
If the requirements are fulfilled, check your Internet connection and configure your security program and Windows firewall to allow the client to communicate. If the problem persists, update your video card drivers, uninstall the game, log in to your Webzen account, download the client from Webzen Download section and install it following the on-screen steps.