MacBook Pro (Tiger): Get keyboard defaults to stick
Based on this hint, you may be able to open System Preferences as the root user and configure the keyboard layout there (which will cause it to become the default).

1) Open System Preferences as root:

sudo open /Applications/System\ Preferences


2) Select the "International" System Preference pane

3) Click the "Keyboard" tab

4) Select the layout that you'd like to use, and quit System Preferences