Trouble setting top-level domains for WP 3.0 sites

I am working to set up a staging environment on for a multisite project on my shared hosting account.

I’ve installed Wp3 on mydomain.com, domain mapping utility (in mu-plugins) with sunrise.php, and set the * wildcard domains within my host.

I’ve set up two new sites on mydomain.com as site2.mydomain.com and site3.mydomain.com, but want to direct my mydomain2.com and mydomain3.com (godaddy registered) to load those sites.

I can get site2.mydomain.com to work properly, but when I set the primary domain for that site to be mydomain2.com, it’s a server not found.

Any help would be much appreciated