I don't know but the same thing is happening to me.
I am logged in, but when I post a reply, it changes to the log-in screen and the messge is gone!
It has happened 4 times to me today!
I re-booted and that seemed to make it work last time, but I don't know what the answer is. I am now copying the message before posting, so I can at least avoid having to re-write it!
Copying Now........