Can Not get Domain Mapping to function properly

i have installed wordpress multisite on my primary domain ( the multisite functionality is working fine as i can see the subdomain in the browser. I then map the domain and now when i paste the subdomain into the browser i can see the address switch over to my domain how ever the page is completely empty. it does not show the default wordpress blog install that i was able to see through the subdomain. I purchased a dedicated ip address for the primary domain as well. I have the WPMU Dev plugin installed in case you would like support access to the site.

thanks for your help,