Urgent problem for Chris!!!
Did you order this as an additional IP and then try to ifconfig it so that you can use it on your Linode? If so, you need to do the following instead:
Log into the Control panel and go into the Configurations menu. Bring up the configuration you're currently using by clicking it's name. You don't need to make any changes here - but you MUST click Save Configuration at the bottom of the page. Then, reboot your Linode with that configuration and you'll be able to make use of the IP(s) that you ordered.
Hope that helps