Note that if you have a period in your MyOpenID "username", such as
awesome.dude.myopenid.com
you must log in by typing in your URL, do not click the MyOpenID button.
It's a long story, but MyOpenID royally screwed up by allowing early users to put periods in their names. Why?
https://dude.example.com
requires a different SSL certificate than
https://awesome.dude.example.com
They no longer allow period in names (they force dashes instead), but early adopters might have them. Long story short, if you have a period in your MyOpenID username, you MUST type in your login manually in the login form. Clicking the "log in with MyOpenID" button will not work for you. Note: even if you type in your login manually it will only work if JavaScript is allowed from myopenid.com. This can happen with JavaScript whitelisting, as with Firefox and NoScript.
Yes, this is a bug that can be worked around on their end (not our end), but I can't get anyone to fix it despite repeated emails to JanRain.