Frame Selected hotkey not working

I am running Unity version 3.5.1f2 under 64-bit windows and the hotkey for Edit->Frame Selected (key F) is not working. If I select an object in my Hiearchy window and then select Edit->Frame Selected from the main menu, the selected objected is framed correctly. However, if I simply press the hotkey (F) nothing happens. Is there something that I need to do to enable this hotkey?

As @robertbu, pointed out in the comment above. The cursor has to be in the scene window for the hot key to work. Thank you.

Op please accept the answer so the question appears to be solved, and other who have the same problem can find it easily. Or write one yourself, if you prefer.