Update -
Mixed news.
Good news - We have seemingly fixed the problem. The forum and the Windows Mobile Training site were only passing information unilaterally (i.e. the forum could tell if you started out as a Windows Mobile Training user, but if you registered for WMT AFTER registering to the forum, WMT didn't return the favor of telling the forum you had already signed up and wanted you to re-register).
We have updated the logic on the server and the two sites are now properly keeping each other looped in about dual membership. I have tested this by creating several new accounts, first with forum, then with WMT and I'm not getting locked out (I did get locked out when I first tested this before the changes were made).
Bad news - Anyone who set up a 2nd forum user ID still has two forum user IDs. Please send me a private message if this has happened to you and I will work with you to determine the best solution for fixing your individual account.
If your ID isn't working, but you haven't created a 2nd user ID, log out of all Live ID applications, clear your cookies, and restart your browser. This should solve the problem.
Thanks for everyone's patience!
-Andrea