I'm having this problem after migrating away from MyOpenID and setting my SE Open ID as primary.
I just tried clicking on theoretical cs and I got the Q&A notification bar. I'm using the 'SE open ID' now as main ID. I think my browser is OK for global auth, I just checked. I'm on Ubuntu Firefox.
First I clicked on 'Log in'
As you can see, no luck.
Currently my meta.stackoverflow profile shows this.