Hi everyone,
This is an issue sporadically for very few users, however we haven't been able to replicate it. However I have now got a Chrome instance (Mac) which is reproducing the error (for some unknown reason), and I hope to not restart it until I have this nailed!
Rails application, using memcached for session store. While the bug manifests in the _app_session_id cookie not being created, our javascript-generated cookie test and app-generated language cookies are being created successfully. This means that InvalidAuthenticityToken errors are thrown for every form that is submitted by those afflicted - people can't log into the app.
The error occurs across all browsers - had reports for IE7 and Firefox (which most users use). Switching to another browser often fixes the issue (though not always), and standard cache-cookie-clear tactics do not.
So now that I have got Chrome open which is having the same issue - in development, staging and live environments (meaning http and https). All other browsers are fine.
I've restarted the servers and restarted memcached. I don't really want to restart Chrome - in the risk that the issue does go away with that (having said that, it hasn't worked for users).
I've been tcpdumping the requests - and although I'll keep digging, I'd love it if anyone had any suggestions, places to start looking, anything. This is really painful ;)
Thanks!