"Have you deleted your cache and the I2 session cookie after this started happening?"
Is this Norwegian techno talk?
I wouldn't know where to find them. I don't know what a cache is and the only cookies that I know about are in my kitchen, hidden from my husband. Seriously.
'kay. What browser are you using? I'll walk you through this but since every browser is different, how you delete the cache and cookies differs form one browser to the other.
BTW: The cache is basically the browser's storage facility, a way of storing parts of web pages so it won't have to load everything anew every time you browse to a page where you have been before. Cookies are specific to the sites you visit and keep track of your browsing sessions at the sites the handle, things like your login info, when and what you did during that session, if you logged off, and so on.
If you keep the cookies, they can remember your login info, your site preferences, etc. They can also be sneaky and do things behind your back if you are unlucky. Most don't but some do.
Anyway, sometimes things get messed up. The browser gets confused and mixes up the cookie info and what part of the cache it should keep and what it should update. Very often it messes up things that have to do with logins and sessions while being logged in. There are lots of reasons to why this happens but usually the solution is very simple: remove the old cache and the offending cookie, thereby forcing their update. All you need to do before you delete them is to log off from the site that gives you problems, to make sure that the cookie(s) and the cache are no longer in memory.
Hmm. I hope I managed to explain this, somehow. There's more to it, obviously, but this should cover what you need to know.