To me it looks like the cookies are expiring too damn fast.
Sometimes I would be creating a course, and by the time I'm done, the session expired, I have to log in again, and the course is all lost.
Or I click on one of my activities, only to see that I don't have permission to see it (that's code for you just got disconnected, log-in again).
I've tried to select the "stay connected" checkbox on log in, but really, it doesn't seem to make much of a difference.