Domain Mapping - Not connecting to domain

Hello,

I'm trying to map the domain "blogdiogogomes.com" to my site (WP MU) "http://virtualmarketingpro.com/blog/diogogomes/

I've followed the instructions but something is wrong and can't figure out what.
blogdiogogomes.com is pointing to the IP of the dedicated server where the WP MU is installed.
The WP MU is installed at http://virtualmarketingpro.com/blog/

When I go to my site and try to map the domain, I always get:
https://www.dropbox.com/s/2mkayxx7ddzz8mp/Domain%20Mapping%20Error.jpg

Can anyone point me on the right direction please?

Thanks,
Diogo Gomes