I am having an issue with domain mapping. My blog has

Hi,

I am having an issue with domain mapping. My blog has the following setup -

http://test.domain.com/ - Main site
http://test.domain.com/site1 - Site 1
http://test.domain.com/site2 - Site 2
http://test.domain.com/site3 - Site 3

Now I want to map http://test.newdomain.com to http://test.domain.com/site3

I have parked the domain newdomain.com in cPanel, setup the subdomain test.newdomain.com to point towards my test.domain.com public_html directory (so it has an A record with my servers IP).

Surely this should be enough for everything to work but it comes back saying 'Domain name is unavailable to access' - are there any other factors that would be causing this?

Thanks,
Chris.