I have been running into problems with multisite domain mapping that I have not been able to solve. I have gone several rounds with hostgator support without success. Here is the scenario:
I have a hostgator account for the URL main-domain.com. It is a new install of wordpress 3.0 configured to have WP multisite capabilies. I then created a new a subdirectory site at main-domain.com/subsite. Everything seemed to be working fine.
I then tried to map the domain "subsite.com" to the subdirectory site "main-domain.com/subsite" using the "wordpress-mu-domain-mapping" plug-in. I have been using the method described in http://ottopress.com/2010/wordpress-3-0-multisite-domain-mapping-tutorial/
I installed the domain mapping plugin as suggested and everything seemed to set up fine. Since “subsitecom" was purchased through godaddy and I went to the godaddy contol panels and changed the DNS "A" record of subsite.com to point to my hostgator ip address of XXX.134.XXX.743. I then went to my hostgator cpanel for main-site.com and created subsite.com as an addon domain (without any redirect rules).
I then went into my wordpress admin for main-domain.com/subsite and set up the additional domain of of "subsite.com” to be mapped to that subdirectory site. That subdirectory site now has two domains listed: 1) main-domain.com/subsite and 2) subsite.com.
When main-domain.com/subsite is checked as the primary domain everything works as expected. The site loads perfectly, the backend is fully functional, and when you navigate in the browser to subsite.com you get automatically redirected to main-domain.com/subsite (with main-domain.com/subsite showing as the final URL).
However, all hell brakes lose when you go to domain mapping admin for main-domain.com/subsite and try to make the change to subsite.com as the primary domain. Specifically, I mark the radio button for subsite.com and hit the "set primary domain" button and then I get a white screen with the following error message:
Internal Server Error
The server encountered an internal error or misconfiguration and was unable to complete your request. Please contact the server administrator, email@example.com and inform them of the time the error occurred
Notice the syntax of the address in the message "firstname.lastname@example.org". It appears to be looking for a subdomain "subsite." I don't know why this is happening.
After this happens if you navigate to EITHER subsite.com or main-domain.com/subsite you get a firefox message that states:
The page isn't redirecting properly
Firefox has detected that the server is redirecting the request for this address in a way that will never complete.
Does anyone know what is going on here and/or how to fix it. Any assistance would be greatly appreciated