I'm using Ubuntu 11.10 and a very novice user.
From today, I'm suddenly experiencing this problem. If I press Ctrl+Alt+L to lock the PC, I find the following error message
Couldn't execute command: gnome-screensaver-command --lock Verify that this is a valid command
and PC doesn't get locked. If I try to lock from menu item "Lock Screen" in the power button at the top right corner of the screen, nothing happens.
Yesterday I updated and upgraded the OS. I think this is the first time I'm trying to lock the PC after update.
What's going on? How to fix this?