When I authenticate to a CalendarServer instance configured to use digest authentication (concerning which I am a compleat newb) using Sunbird or Lightning, wait fifteen minutes, and attempt to, say, refresh, I get another authentication prompt. This doesn't seem to be Sb/Ltn-specific: the same timeout-and-reprompt happens when accessing the calendar URI with a browser, including Opera on Linux and IE on Vista (though not with IE 5.2 on Mac OS) - so it doesn't seem to be specific to the Mozilla network stack, either. Wireshark shows that after the 15-minute timeout CalendarServer responds to a query with a 401 challenge and new nonce value in the WWW-Authenticate header - but that header does not also include a 'stale="true"' as I would expect from my (possibly naive) reading of RFC 2617. So I'm suspecting that this is a CalendarServer bug rather than a Mozilla one, and I'm hoping that someone more familiar with digest authentication than I am can comment. bb