Keyboard Layout Question

In System Preferences/International/Input Menu/ I have selected four keyboard layouts: British; US; French; German. I have also checked Character Palette and Keyboard Viewer. Of course I can switch languages using the menulet (Flag icon).

Can anyone explain why the keyboard layout gets altered (every once in a while) though I have not selected any change from the keyboard options on the menulet? I suddenly find I'm using the US keyboard when I haven't checked out of the British version.

I know that hitting Command and Space keys will do this, but I'm talking about the computer making these unintended changes.

Someone will correct me if I'm wrong, but I think applications "remember" the language you last used with them.

So if you use Safari with French and Mail with British, switching between the two will cause the layout to switch as well...

I might be wrong though...

Hello Aptmunich: Thanks for your advice. How can I get applications to "forget" the language last used and stick to the British keyboard at all times - unless I make the switch manually?