1. Try another browser.

2. Try another computer.

3. Do not use email from the black list.

4. Make sure your do not use special characters in your username (; : , # spaces / $ []{}_ -$%^&*"' etc)

5. Try to lower  your browser security level (e.g. Tools>Internet Options>Security)

6. Clean your browser cache.

7. Remove all captainsim cookies.

8. Make sure your browser accepts cookies from captainsim.org.

9. Check your antivirus/firewall settings.

10. Check your Windows User Account Control settings.

If that does not help, there's nothing else we can do, unfortunately.