Someone else suggested using Mission Control, when launched you add your screen, a copy of your screen. You delete the older one on the ribbon, should say "screen 1" the one you add will say "screen 2. that one you keep. It worked for a while.
I had (2) users, my wife and me. About 2 to 3 months ago, I deleted her user account. She went back using her Windows desktop. Still had the same problem, not as often, A couple of days ago on a apple forum, some one suggested deleting com.apple.loginwindow.plist in/Library/Preferences/Xsan and deleted this to trash and in User/LIbrary/Preferences/com.apple.loginwindow.plist and deleted that one to trash. Reboot, when mac loads you see a couple of dialog boxes looks like a new install, you see your wallpaper in a fuzzy background continue on both, and the mac shows your apple ID you put in your password, and VOILA!! you have your desktop is back. All it is doing is recreating new files and replacing those (2) files in their proper folders. You can then delete the old files in the trash. Do a reboot to test it. Those files, I think, still had (2) user info and never was cleared,
