mapping to the main domain

Okay, this may be obvious and I’ve done it before (perhaps I’m too hungry to think right now) but I want to ask and maybe over lunch I’ll get an answer. 🙂

I have domain mapping set up and just mapped a new domain to a subsite, no prb. But I can’t figure out how to map another new domain to the main site of the network. It is going to the network site registration page instead of public_html.

Main domain: http://coccoyoga.com
Prev mapped domain (works) http://grumpyyoga.com
New domain (doesn’t work): http://yogaforskeptics.com

Is it something in the config file for the main domain?

Thanks!