It usually happens when I have my browser opened for a long time and if I close it and turn off my computer and later turn it on again, and turn on my browser, I can see that I need to login to all sites again. Although this happens not everytime I do this. It happens just sometimes, but this week, it happened for the third time already. Sometimes It happens even without closing my computer, I just close my browser, later turn it on, and I can see that I am logged-out from all sites that I were logged-in before. I have the latest version 30.0 and only 1 add-on activated (alexa toolbar).