Something really weird. Opera had a nervous breakdown and did some random things. Then I saw a message that I had been 'unsubscribed from the forum'. Then Opera melted down completely while I was typing a post. When I got back on-line (with a different browser) I discovered I had been unsubscribed from every forum I was following.
Edit: Now not sure about the above. Something strange definitely happened and I seem to have been unsubscribed from some forums but others appear to be working. As far as I can tell it is normal again.