iCal DAV The Server Responded with an Error (HTTP 302) after sleeping
Several things could cause this, but you could eliminate or reduce the chance by doing any or all of the following:


Turn off all networking before sleeping.
Reduce the refresh time period for that calendar to avoid it refreshing while the system is waking or getting re-connected with an available network.
Quit Calendar before sleeping.
Move the calendar to another hosting site (assuming it's not really the Mac that's causing the http error.)