This happens only when I use my Bookendz dock. I push my PB all the way in (it is alseep), it wakes up (lid still closed), 2nd monitor is made my primary display, 2nd monitor has no wallpaper, open PB, click "Detect Displays", 2nd monitor now has right wallpaper, PB LCD has no Wallpaper. System Prefs shows the right wallpaper and when I change the fillature of the picture or change the picture and back again, my wallpaper reappears.