Thank you for your post.
The first thing you want to do is restart the FileMaker Server Service by running "fmsadmin restart server" in Command Prompt (running as administrator) or Terminal. You may also achieve this by rebooting the machine.
FileMaker Server 9 requires Java 6 update 7. If you have updated Java, then you will have issues with the Admin Console.
You may also reinstall FileMaker Server 9. This would resolve any issues the software may have gathered over time.
For more information check out the FileMaker Server 9 Help Guide.