The information below is how to configure your router to update www.ChangeIP.com dynamic dns hostnames:
substitute your account setting for those in quotes
DDNS Service Custom
DYNDNS Server nic.changeip.com
User name 'Your ChangeIP.com username'
Password 'Your ChangeIP.com password'
Hostname 'Your DynDNS hostname' or '*1' for Group #1
URL /nic/update?system=dyndns&hostname=
Additional DDNS Options --ip_server_name ip.changeip.com /
I had tested the configuration and I can confirm the configuration for changeip.com works.
If you are sure that you have followed EXACTLY (you need to double check) the configuration (e.g. 'URL' and 'Additional DDNS Options' fields ), and if it is the first time that you tried using DDNS feature for your DD-WRT router, then I believe there is certain bug in your DD-WRT firmware.