I had the same problem and renamed the folder to badbetter-wp-security and then was able to logon with the wp-admin
then I went and deleted the damn plugin
Hope this does not screw me up. I am not any sort of a programer just a ordinary guy trying to have a basic blog and this is a big time waster.
I am royally pissed at Ithemes for this ah…. upgrade
Ithemes is totally silent. I will have a problem trusting them again their customer support is totally non existent on this issue.