I've got a mapped domain on a multi-site install that is working fine. I'm trying, however, to use a subdomain of that mapped domain for another application (a listserv). In WPMU 2.9 I was able to do this. I was using the mapped domain plugin and I just added the domain on to my host and then set up a subdomain. When I installed the application in the corresponding directory, it worked.
However, since upgrading to 3.0, I can't get this to work. The main mapped domain is working fine, but when I try to access the installed application at the subdomain I get the following message:
"No site defined on this host. If you are the owner of this site, please check Debugging a WordPress Network for help."
Any ideas how to fix this?