Sometimes, such as when an email validation or a password reset is required, the login session can expire before there is time to respond. Once the session has expired there is no simple way to start a new session as refreshing the page still carries the same token and it seems that you need to restart the browser (possibly going back to the original URL will start a new session) to create a new session.
Ideally the length of time for these events should be extended to allow completion. Additionally a link, or better still a button, on the session timed out message dialog to automatically start a new session would be very useful in order to make the process as easy as possible for user.