mozilla-1.4-2 menuAccessKeyFocuses won't

[ghwb <ghwbush@earthlink.net>]

I'm using unstable/testing, with mozilla-1.4.  I'm trying to set the 
Alt-key to access the menu, instead of the F10 key.  I have set this 
preference in the about:config list:

user_pref("ui.key.menuAccessKeyFocuses", true);

However, the F10 key still does the focus and Alt does not.  Any 
suggestions on how to get this working?