We had some discussion about this on nl: since several people have related problems recently.
Yesterday I experienced this on XP - MSIE 6:
A page was clearly out of date, the last edits I saw on the history page were not showing. Refresh didn't work. So I cleared the whole MSIE cache.
Low and behold the next refresh produced a page that was even older than the one I already had. Missing all updates after Feb 28 (It is our 'Village pump' page, updated frequently).
Might it be that one of the squids does not realize its content is obsolete?
Erik Zachte