This too was happening to me a few months back ... thought it was a problem with the site servers, but alas finally found it to be totally on my end of things. If you are using Firefox, and some pages are not refreshing sufficiently, try the following:
After loading the affected site, simply type "about:config" in the locator bar, and click ok on the warning. Then type "browser.cache.check_doc_frequency" and check to see that it is set to "1" - if not, double click and change the value to "1" and restart Firefox. Mine was set to "0", and it was not performing any page refreshes.
What's still a mystery to me is how that setting got changed to a zero in the first place.