Preseeding - keyboard-configuration issue

[Richard Owlett <rowlett@cloud85.net>]

http://www.debian.org/releases/squeeze/example-preseed.txt 
[among several other examples] in part gives
</begin quote>

# Keyboard selection.
#d-i console-tools/archs select at
d-i console-keymaps-at/keymap select us
d-i keyboard-configuration/xkb-keymap select us
# Example for a different keyboard architecture
#d-i console-keymaps-usb/keymap select mac-usb-us

<end quote>

When I use it in my preseed.cfg I get an error message.

ERROR MESSAGE TITLE  ---
     Configuring keyboard-configuration
ERROR MESSAGE TEXT   ---
     Please select the layout matching the keyboard for 
this machine.

I choose the first of many options and the install proceeds 
to a successful conclusion.

What is missing in the preseed.cfg file?
TIA