If the trick of resaving the domain info doesn't solve problem (and that takes 15-20 minutes to take effect) then you will most likely need support.
What the error means is the DNS for the site is pointing to an IP, and the apache instance at that IP doesn't have info about the requested URL.
Normally the wiki solution of re-saving the domain will cause the httpd_conf file on the server to be corrected.
Was support in the process of moving you to a new server or new apache instance or anything? If so, this error could work itself out still, but if nothing was already going on with support I would definitively put in a ticket asap.