Yeah, for some strange reason people are having problems with their sessions files. It only effects a small number of users though. To keep it from happening you'll need to stop using 'Continue where I left off' in the options page or delete the sessions files every now and then. If you are really into the session feature I recommend using Session Buddy (on the chrome store) and the 'Download Chrome Extension' on the Opera store. Install the latter one first and then Session Buddy. Its a much more full featured session system.
