This is something I get when visiting the zoog design messageboards, If I spend say more than 40 seconds typing a message, or reply when I post it I get a message saying "invalid session" and lose the text I just typed.
What I do, and new users who get the same problem may not know about this, is to use the "back" button on internet explorer, copy what I just typed, log in again, paste and submit the text fairly quickly - normally if you submit within about 40 seconds or so it is ok....
I have to do this almost every time I post, but a new user might just try a couple of times and give up thinking there is some reason they cant use the site. I know Vincent V gets the same problem - how many others get it?
(this message I had to go back, cut, paste submit as described above!)