10-22-13 11:45pm EST Everything should be working again.
10-21-13 2pm EST We're having Flickr API issues again and will be working with Flickr to resolve it. During this time the photoSync tray icon will appear as offline and you will not be able to sign in via the app. You do not need to do anything. Once service is restored by Flickr, photoSync will start working again. Do not sign out unless you want to do a initial down sync again.