I have my style set to 'Kitchen Sink', which is fixed width.
When I return back to the site after a while (what I'm presuming is the cookie / logout timeout).
Upon first load it loads the full width style....then reverts back to my fixed with choice after a few seconds (presumably when the page has fully loaded).
Not really a bug per se, more of a bugbear / annoyance. A layman's view would be that the forum is applying my chosen style last....