Yes, this is happening to a lot of us and DPR knows about the issue. It's something that has resulted from the security measures taken during the attacks. It should be fixed, but DPR asked that I let him know if it's still occurring in a few days. For now though, he's aware of it and there's no need to worry, as frustrating as it can be to get randomly logged off! (and before anyone says it - there's also no need to worry about the fact that you get a 3-character captcha. it's happened before and is nothing to get freaked out about. just reload the page and you'll get a normal-length captcha.)