Also, make sure you type "su" (super user) to have the permission to edit and save the file.
I suggest you try the following:
$ su
# vi /home/zaurus/Settings/locale.conf
move your cursor to the "ja", and press "i" to go into "insert mode"
type "en" and use backspace and cursor to remove the "ja"
hit the close button (X)
type ":wq" and press enter
then reboot.
Hope this helps