If changes to your WHOIS contact details or nameserver changes don't seem to be taking effect or you receive a "Domain Status does not allow this operation" message it is most likely that your domain name has the registrar lock applied.
The registrar lock is protection against unauthorised transfers of your domain name and also prevents changes to your details. You can easily disable the lock:
- Click "My Domains" above,
- Click the "View Details" button next to the appropriate domain name,
- Untick "Enable registrar lock" and click "Save Changes"