URGENT diagnosing domain mapping problems

A site (http://www.directcomposer.com) trying to connect to my server/multisite is down. Here is what I've found so far:

* In domain mapping settings, site is listed as invalid health status
* IP address entered correctly with client's registrar
* connecting to my server via terminal, traceroute lists my IP address:

traceroute to directcomposer.com (, 30 hops max, 60 byte packets
 1  einstein.cre8tives.org (  0.033 ms  0.013 ms  0.012 ms

* ping also shows resolution to my server

What other steps should I take to diagnose and resolve this problem?