I delete my cookies and browsing history daily. This is something that just started happening about a month or two ago. I thought it might have something to do with my forum settings, but this new layout doesn't even give me access to my user panel or anything.
I am about to shatter your sanity. Then I'm going to destroy you.
I had something similar to this happen to me, only in one section of the forums. Clumsy told me to clear out the cache and that worked for me. I logged onto the forums, cleared the cache and everything went to the way it should have been.