After rebooting, you might have to wait for 5 minutes or so in order for Billboard to be started. It's started very late in the boot process (nothing I can do about that, and it's actually a good thing), because all the other apps (e.g. camera-ui, messaging, etc..) have to be prestarted first. You can have a look at the "top" or "ps" output right after reboot to see all the stuff that happens behind the scenes on boot!