Domain Error (CNAME)

My forum is fireborn.forumotion.com
My redirected sub-domain is http://forum.fireborn.lady-of-winds.co.uk
lady-of-winds.co.uk is my personal domain from 1&1.

I set up the CNAME, DNS and other things so that in the personalized domain space it says that the redirection has worked. Yet when I type in http://forum.fireborn.lady-of-winds.co.uk into the address bar of my browser after 72 hours of waiting, I consistently get the same error message. The main page of the Forumotion website comes up and says "forum.fireborn.lady-of-winds.co.uk could not be found!" The forumotion link still works fine and the website is usually the first option among the list of possible sites, but it's still extremely annoying. Is the problem because it is a sub-sub-domain of a website? Or co.uk? Or some other unrelated issue?