Any idea why the keyboard shortcut "Command + `" (press Command key and backtick at the same time on keyboard - backtick is the key to the left of the 1 key underneath the ~) to cycle between open Mathematica windows would not do the expected - computer just beeps when I try? This works on Terminal windows and the Mathematica "Keyboard Shortcut Listing" window shows it as the "Cycle to Next Open Notebook Window" but nothing happens other than a beep sound. Is there some "defaults" setting that Mathematica needs or something??

Have also tried Command + F6 also - just beeps the same as the Command+` shortcut (found this command on the "Keyboard Shortcut Listing" webpage (at Keyboard Shortcut Listing ).

Thanks...