My experience seems to be somewhat different than what others are describing. In particular, it's only been happening for about the last 8-9 days, while others have been seeing it for a few weeks. What I'm seeing: for *some* pages on disboards, I can log in, and when the new page loads, it already shows as not logged in.
The odd part is that this only seems to happen on certain pages. In particular, it seems to only happen on page one of certain forums. It will show me as not logged in, but when I click on a thread, the topic opens and *that* page shows me as logged in - time stamps are adjusted, I can reply, and so on.
Also, lately the problem has become intermittent. I can log in to the restaurants forum and the login will sometimes "take", sometimes not. But the individual thread pages seem to always detect the login.
It's a curious issue indeed.