I was always using my Google Open ID account to get to stack overflow, but since I have to use 3rd party internet access and would prefer not to store google cookies on those machines.
I thought it would be a good idea to create stackoverflow registration and use that in less secure environments, in case cookie got stolen I would not get Google account compromised (no offence to stack).
I can complete registration, then get confirmation email, then confirm it. When I confirm registration I get to Registration successful page, but when I try to log in using stack option, I get this.
I can go through registration process multiple times, get multiple confirmation emails.
One thing I am doing that might be 'out of ordinary' I am registering on chrome on laptop, but confirming on my phone.