Unexpected Firefox Software Installation for Language Packs

[scar]

I have been getting a strange pop-up lately when i start Firefox, asking
me if i want to install some foreign language packs.  I'm in the USA,
and Firefox is wanting to install language packs for en-GB and en-ZA.
Initially it was only asking for en-GB and I didn't think anything of it
because Firefox was recently updated.  So, even though I clicked
'install' it still asked to be installed whenever i restarted Firefox.
en-GB shows up in my Add-ons/Languages, and if i click on 'Disable' and
restart Firefox, it just keeps saying en-GB "will be uninstalled when
Firefox is restarted" no matter how many times i restart.

Now it is also wanting to install en-ZA.  I never explicitly told the
system i needed these languages, but somehow the extensions ended up in
/usr/lib/firefox-3.6.24/extensions.

How did they get there?
Can i just delete the xpi files from that directory?
Is something malicious going on? Why is it still asking to install en-GB
even though i already clicked 'install' and now it's asking for en-ZA?
And why won't en-GB uninstall from within Firefox

I'm  using Ubuntu 10.04 LTS with Firefox 3.6.24
here's a screen shot of the pop-up: http://i.imgur.com/a4lSg.png
and here's the xpi files if someone wants to inspect them:
http://www.sendspace.com/filegroup/DGZPzIU4zb%2FLXdEWGxwUTQ

thanks