I am trying to use domain mapping to add more domains that should point to the main domain. The install is in the root of the main domain progressivesolar.ie.
Domain mapping is working for a domain I mapped to one of the subsites http://www.braunbauzeichner.com about a year ago - but now when I'm trying to add additional domains (progressivesolar.co.uk, etc.) so they just point to the main site, the domains aren't saving when I try to save under 'Domains'.
I installed the Development version per Ron's suggestion and still no luck. I don't want to try changing to using CNAME (not even sure what I'd do there) as it is already working for that other site that really needs the domain working for it.
On the control panel all of the domains are pointing to the same ip address and have web hosting set up pointing to the WP installation -- as is the domain that is working. If you go to http://www.progressivesolar.co.uk you'll see that it points to the site, but gets an error.
The site is on WP Version 3.0.2 using Genesis with a child theme I customised.