thanx
You probably mean en-US.
This is a known issue and I think people are working on a fix.
Because extension dependencies is still not a well-understood thing (I
think some support managed to get into Firefox 2?) and getting the users
to install the right things to get a locale to work is still somewhat
confusing. Well, that'd be why I'd do it, anyway.
http://wiki.mozilla.org/Extension_Manager:Extension_Dependencies
--
Mook
mook dot moz plus stuff at gmail dot comintern