WordPress MU

I have seen my mu site today and i only can read this:
No WPMU site defined on this host. If you are the owner of this site, please check Debugging WPMU for further assistance.

I have .htaccess and wp-config.php fine... i have 300 users.. :S what must i do?

Thanks!!!

have you done a search for that error yet here in the forums? That would be my first step.

Yes, drmike, my wpmu was defaced by a cracker... i have lost all my db and cant restore my backup...