Shortcut for lock screen doesn't work

[cube3x3]

Hi all,

I have just installed the compiz fusion on my intel 945gm
its working great at now..
but i have one problem with it - shortcut key for locking screen doesn't work
Key is 'Control + Alt + L'
It doesn't work for me.

Any ideas???

Update::: I found the command for that 'gnome-screensaver-command -ac'
Then i tried to put it into command0 in compiz settings with hot keys as 'Ctrl+Alt+L' - but it doesn't work
Then i changed the key to 'Ctrl+Alt+M' and it worked.
So please can some one tell me which plugin uses 'Ctrl + Alt + L' key so that i can disable it.

Thanks