No, this is by design -- myopenid, like Google/Yahoo/AOL, no longer requires the username, so it's one less step for the user when we omit it.
works perfectly for me, I can log in with that, and that's what the login page does now.
The only time this would be required is if you have multiple myopenid accounts -- in that case, enter the URL manually on the login page like so:
(you can omit the http part)
edit: that said, myopenid does have a bug in the way it handles user names with periods. They no longer allow usernames with periods and are still (as of this writing) working on a fix. If you have a legacy myopenid username with periods, you must enter the OpenID URL manually (eg as a complete http://example.myopenid.com URL).