If I go to Gnome's System menu-->Control Center-->Popup notifications, and try to Preview there how I've set notifications (click "Preview" in that dialog box), this is what is popping up on me, but it's not doing it every single time (just most of the time):

Any clue how to narrow down issues with system messagebus? Or is this a dbus thing?
Edit: If I knew where the settings for Popup notifications are in Gnome, I'd reset that folder and retry. Anyone know?
Thanks.