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I was logged in SO and there were some new notifications in my inbox so I clicked one that led me here but I was not logged in. Never happened before.
Using chrome 21.0.1180.57 on OSX
I am unable to reproduce that behaviour.
You can visit the Network Login Troubleshooting to check for the availability of certain necessary features in your browser in order to have the network wide auto-login functioning properly.
This may also apply to your issue.