It's still happening. Roughly a quarter of the time that I click a link to a thread I get the login screen and after logging in again am then returned to the top-level forum page, from where I have to click two or three links to get back to where I was before being logged out, with the random logout happening again anywhere along the way back. It's making the site pretty difficult to use. It suddenly started happening a few days before I posted at the top of this thread, and I hadn't made any changes to my browser setup, cookies, etc.