I'm on the newest version of wordpress: 3.5 and the latest version of this awesome plugin: version 4.1
I've noticed some error logging in the script and they all look like this:
Error number: 8
Error type: Run-time notices. Indicate that the script encountered something that could indicate an error, but could also happen in the normal course of running a script.
Error Msg: Undefined index: administrator
File name: wp-content/plugins/stop-spammer-registrations-plugin/includes/stop-spam-reg-checks.php
Line Number: 46
It doesn't happen all the time but it does log these errors now and then, up to 20 a week or something.
Should be easy to fix I suppose, just another check before assuming things.