shorcut keyboard problems for camera controls

Hi - does anyone have probs with the keyboard controls for 'take snapshot to disk' on a Mac. It should be Cmd-` but it doesn't work. I hold down Cmd + the Shift button + `
(the shift is for the accent grave) but nothing happens. All other keyboard shortcuts I've tried seem to work.
Mac OS X 10.4.8.
I've tried different keyboard settings - no luck. Any help would be much appreciated.

its bugged... they screwed up and forgot to make it CMD, its CTRL even though the shortcut says CMD ` its CTRL ` and it works.