OpenID Broken on WordPress.com [Updated]

1. February, 2011

If you’re trying to use your wordpress.com blog to login to some site via OpenID, you’ll see this error:

Unable to log in with your OpenID provider:

Cannot decode Key-Value Form because a line was found without a ':' character. (line 3: '<head>') 

See also:
http://meta.stackoverflow.com/questions/76841/cant-log-in-using-wordpress-com-openid

http://en.forums.wordpress.com/topic/openid-not-functioning

[Update] According to the WP support “We have corrected a glitch and the problem should no longer be occurring.”

At least for me, it works again.