I have had my mini mac for over a year now, but of late I can't get the Desktop Background to retain. I can change the background picture and this works, but when I shut down or log off and log back on again the background has reverted back. I have tried moving the desktop.plist to the trash but this has no effect. The only way I can seem to get the new background to retain is to turn the mac off with out logging out or shutting down. Any suggestions.