I spent (wasted) a lot of time trying to register for the Forums both through the website and in-game. I gave up for a while, after another player suggested it was being worked on.
Then I happened to see a link on my Turbine account page about registering for the Forums and it worked.
If you're going to disable registration through website and in-game MyDDO, please do it properly, and give notice when those links are clicked that direct players to do it through their Turbine account management.
Thank you.
PS. I did a search and could find no mention of this issue in the forums.