I've included a link below, to the issues, I identified with the "Social Login" plugin:
On my second comment, you can see I've included information about the "Social Login" plugin causes this plugin to permanently change the username field to be the user's email address, so that their username is no longer available.
I've also noticed that some of my earliest registered user accounts are having this same issue, even if they don't try to log in via Facebook/Google.
This plugin shouldn't change the username to the email address, it should allow login via username and/or email address. This is quite cumbersome to deal with, especially if you deactivate the plugin.
As it is now, the username associated with the administrative account on http://bamajr.com/ no longer has a standard username. The email address has replaced the username. So when this plugin is disabled, this user cannot login.