The same happens to me...and I am not using any cleaning apps.
Everytime I enter for example a forum page (opera forum incl) and have been logging in before...it still opens NOT LOGGED IN. Very annoying and I thought Opera would have fixed this by now.
Now it annoys me so much that I uses other browsers when I need to enter forumpages...Imagine how embarrassing ...entering Opera forum and need to use Sleipnir browser...:-(