Did you try any Stardock applications recently? This is a well known problem - things like object bar (and others, I'm not sure which ones) run their own tray server application that grabs all the icons before LS can get them. You'll see a tray-something-or-other.exe running if you look in the task manager. Get rid of that (edit registry startup items, or uninstall it) and the tray icons will reappear.