Zope/Plone 2.9 strange session behaviour?

This is what my server is running: (Zope 2.9.6-final, python 2.4.4, linux2)

I have a log-in form whe开发者_Go百科re user have to authenticate to the system. The Session expires after some time (say, 20 minutes).

If I am on a page (call it x) and my session expires (mean that when I click on a link, I will redirect to log in form) or I restart the server manually something strange happens: If I log-in again and click on some links (say all but not x) the page will be sended to me. If I request the x page (where I was before the session expire) the server redirect me on the log-in page (like I have no permission to access that page).

If I disable the cache on my browser, that problem seems to disappear.

Anyone knows what happening?

I've seen problems where the 401 redirect ends up being cached by proxy caches. Plone 4.1 now sets appropriate cache headers to avoid this.