My DCS-2310L sometimes does the same thing after I change the event settings, until I reboot. I found the best way to prevent this from happening is after you change event settings, reboot the camera (either via Reboot in the menus, or unplug and reconnect power). You shouldn't have to do this, it may be a firmware bug, but this is what I'm doing to make sure I get current pictures instead of pictures of the previous event.