What miniman said, Dee.
This happened a while back with one of the upgrades or something. We had to delete our cookies on our computer, which websites use to remember you, then log back in. You will need to log back into every site whose cookie gets deleted, but it's just easier to delete them all because some you don't want anyway.
Open your browser, which it will be if you are reading this (lol). Click on the Tools button. Click on internet options, then look for delete cookies, browsing history... something like that. This is in Internet Explorer, btw.