can't post comment with openid login

I try to leave a comment on my friends blog, which uses intensedebate for comments (http://nano.rulix.org). I already have intensedebate account and I want to use it to authorize.

- I click on "Or post using OpenID" link.
- I enter my openid url
- I click on "Submit comment"

And now I get this message: "Dear OpenID user, unfortunately your provider did not give us all the info we need. Please fill in your credentials below to proceed!" and I need to enter my Email and Username.

What the hell? I already entered Email and Username during registration. I don't want to do it again!

OK, I try to enter them, but I get messages "This username is already in use" and "This email is already in use". Of course, they are in use, they are used in my account, and I am trying to login to it!

I made about 7 tries, and actually one of them was successful - I managed to post a comment. But I can't repeat it even at the same browser session.