BLZ51900002

The computer couldn't connect to the login server because a security program was blocking the connection, or because the connection was unstable.

1. Close all other applications to resolve software conflicts and free up resources.
2. Configure your security software's exception list to allow Blizzard applications to run.
3. Reset your network devices to resolve local connection issues
4. Release and renew your IP and flush your DNS to resolve any network conflicts.
5. Run a security scan to remove any viruses or malware infections.

Tried everything here?

If the previous troubleshooting steps didn't resolve the problem, you can ask the Blizzard player community for help on the tech support forums (if available) or other community gaming sites. Local computer or network technicians may also be able to help if you've exhausted all other resources.