Keyboard shortcut Command-~ DOES NOT WORK in/on some apps/machines

Question

It seems that in Mac OS 10.6.2 the keyboard shortcut "Command-~" ( a.k.a.
"⌘-~" or "Command-tilde") is quite fickle. It is used in most apps to
switch between open windows within an application. It was available in OS
10.5 in Safari, Microsoft Office (including Entourage), and most other apps
with the capacity to open multiple windows simultaneously. But in OS 10.6.2
this shortcut is available in Safari on my 2.16 GHz Core2Duo 20" iMac but
NOT on my 2.4 GHz Core2Duo Unibody 13" MacBook; it's available in Entourage
on my MacBook but NOT on my iMac. So it's available on some apps and some
machines but not on others, there's no rhyme or reason to it, and it's not
consistent between like machines and apps, which makes me think that there's
a system-wide preference or command that could turn this on and off. I
thought perhaps it was controlled by a preference in certain apps, but I
have found no such prefs. Is there a way to control this - in other words,
to make it available where it currently is not? Or is there a command to
make it universally available on any 10.6 machine (my preferred solution)?
Thanks for any help offered.

Answer 1

Not a reply to this specific question, just a quasi-relevant comment that might help some folks.
In Leopard, and with (for example) English and Russian chosen in System Prefs under "Language" and the keyboard shortcut set to command+space, I would always see the flag change in the menu bar as soon as command+space were chosen. Now, under Snow Leopard, hitting command+space seems not to make the change. But it does make the change, you just need to take your fingers off the keys first, then the flag will change.