Had it a couple of times today, once when trying to read this thread, and I've had it once before, last week. It seems that it is a server issue, but I'm not sure whether that would be the host server or the web server.
When I access the forum, I see &sid=0123456789abcdef0123456789abcdef (or whatever my session ID is) in the URL. I don't think that was the case with the old domain. I would have thought that the session ID would be stored in a cookie and not as part of the URL.
"We are the Queen's shield. We are the nation's shield." —Sir Nicholas Fury, 1602