I would make your email and your openid url all lower case. and make sure the email in the mojoportal account is the same as the email address attached to your openid. When you try to login with open id, if the email address returned by openid is not found in the db it will try to create a new account and log you in, but if the openid is already attached to an account with a different email it will fail as you describe.
Hope it helps,
Joe