I've recently done a minimal install of ubuntu 12.04 with lxde. I can't get it to check for updates on boot. Under "Desktop Session Settings" I have checked Update Notifier to be an automatically started application, but it doesn't seem to work. Even when I open Update Manager it will say that I have nothing to install. But then I click "Check" and a bunch of things will show up to be updated. How can I fix this?