WPMU sub-sites down

PANIC MODE! (But my head is still attached.)

All of my sites are down except the main one. The main one with the WPMU installation is beachheadcommunications.com. One subsite is meshmarketer.com.

The IP address for beachheadcommunications.com is 64.142.108.209. Meshmarketer.com resolves the IP and the IP can be pinged, but the site doesn't come up. There is also an error:

Not Found
The requested URL / was not found on this server.
Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.
Apache/1.3.41 Server at meshmarketer.com Port 80

I have checked the A records and it looks just fine. I have made no changes recently.

Any help?