I'm using Fedora 15 with Gnome 3 on my laptop. I don't restart the system unless there's an update that requires me to, preferring to use the Suspend feature instead. However, I noticed that after an uptime of a few days, the screen doesn't lock anymore. Neither the shortcut 'Ctrl+Alt+L', nor the terminal command 'gnome-screensaver-command --lock' seem to work. I'm sure restarting the system will enable me to lock again, but I don't think I should restart just to get this feature back.
Does anyone know why this happens? Is there some other way to lock the screen?