Where I work, We've got a HP Pavilion a1440n that is acting as our server (it's a small business). This morning everyone lost our network connections and when I brought the server out of it's screen saver mode all it had shown was a black screen with the mouse still being active. I didn't try to see if CTRL, ALT, DEL worked. I simply just restarted the computer and it is now running fine again.
What I want to know is what would have caused it to do that.