Domain Mapping using subdomains?

Hey,

running latest version of domain mapping plugin with wp 3.1 i wonder if mapping subdomains to a blog doesn't work?

Let's say my network runs on blognetwork.com setup with subdomains. One of my blogs called live.blognetwork.com should now be reachable via live.mydomain.com so i enter live.mydomain.com into the domain mapping plugin. Domain and server all setup i get the message that i need to create a new blog when calling live.mydomain.com. This means wordpress thinks it doesn't exist.

Seems like the plugin doesn't work right... anything i missed in the setup?