Hi everyone, hope you can help. Starting yesterday, when I come into work and turn on my 24" iMac (running 10.7.5), my desktop wallpaper image has reverted to the Apple swirling galaxy picture, and the three network drives I keep on the desktop have vanished. It's not a crisis; I just go "command + K" and I can put them back in a few seconds, but it hadn't ever happened before yesterday. Any ideas?