Great start Puntuado con 4 de 5 estrellas
The language pack is pretty good. People, this is not something that helps you to type in Malalayam. Rather, a "language pack" is an extension (add-on) that changes the language of the user interface in a Mozilla application (Firefox, Thunderbird, SeaMonkey, etc.). Please see this screen-shot taken from my system - http://prntscr.com/1tt8chTo enable Malayalam Language pack, add the extension to firefox, type "about:config" in the address bar, override the warning, search for "general.useragent.locale", right click and select "Modify", change the value to "ml". (Prior to that save your current preference). You can see the ".xpi" file in your profile folder >> "extensions" (most probably, the profile folder will be at %APPDATA%\Roaming\Mozilla\Firefox\Profiles\). Or you can use the locale switcher add-on after adding the Malayalam language pack (https://addons.mozilla.org/en-US/firefox/addon/locale-switcher/). And yes, don't forget to restart firefox afterwards.
Further details: http://kb.mozillazine.org/Language_packs
To type in Malayalam WITH EASE, you can install "Google Input" on your system (http://www.google.co.in/inputtools/windows/). There are many packages available for Linux as well.