It shouldn't have anything to do with cookies. We only use cookies to store your session (wether you are logged in etc). Oh, we also use it to keep track of which sub-forums you have opened on the front page. But nothing to do with Robertmee's problem described above (as far as I know).
I think the issue has to do with browser caching, I'm gonna try and replicate the issue here and if that works I might be able to find the cause and solution.