Okay, it's twice now I've had this problem:
I spend some time working on a post. I leave it to come back later and finish. When I come back, finish up, and hit "post", I get a message that says my submission can't be posted because I've logged in since I started it. It says to use the back arrow to log in again and then post.
Except using the back arrow doesn't accomplish a thing. In order to post, I have to hit the "reload" button on the browser....
which wipes out my post.
I used to do this a lot while working on story chapter submissions, and didn't have this trouble; it's only been since the upgrade.