I am also unable to register my game - bought through Steam - on the 'Register Game' page. I was able to use the code Steam provides to register on the 'Promo codes' page.
If anyone knows how to resolve this issue could they please us know?
EDIT -- I have found a work-around for the problem. 
In Steam, when you go to launch the game choose instead to open the launcher. Then open up the Configuration tool via the launcher.
This will take a few moments to perform system scans etc, but when it has done click the 'Game' link on the menu at the left. You should see a box labelled Product Keys, and listed there should be your CD key.
Simply input this code in the Register Game box and you will be able to successfully register your game.
Modifié par Aenaryn, 08 novembre 2009 - 10:10 .