Can't Access Multisite Back-ends

I had multiple sites installed on WP 3.0.1 and everything has been working fine for weeks. This afternoon, our servers HTTP service was down for about five minutes, when it was restarted, WordPress is giving me 404 errors when trying to access any of the site’s backend areas.

I can access the main backend, and all the sites are up and running, but something isn’t registering any of the sub-domains.

.htaccess hasn’t changed and the DNS wildcard settings haven’t changed.

Any ideas? Thanks in advance.