Some of my friends commented that they were having problems with TypeKey & making comments.
1. Click the link to sign in.
2. Log in to the TypeKey site with your name & password (you may need to register).
3. The window will close after you login, but my site may still say "login".
4. Hit the refresh button on the window.
5. You should be able to enter comments now.
I'm not sure why its quirky like that, but it works.
Email me if you run into problems.
There's a known problem with TypeKey sign-ins & IE, which I believe is fixed for the upcoming version of MT. If you don't have any accented characters on your blog, I think you can work around it by going into your mt.cfg file and changing "PublishCharset utf-8" to "PublishCharset iso-8859-1".