addon doesn't show up Rated 4 out of 5 stars

I've got Thunderbird 3.1.11 (on Ubuntu 10.4) and I downloaded Enigmail 1.1.2. Then clicked on Tools>Addons and then clicked on the button [Install...] to find the extension I just downloaded. However when I clicked on the downloaded extension and then clicked Open nothing happened. Ie the extension didn't appear in the Addons window. Is there another way to install this extension or have I got the wrong version perhaps? I've used Enigmail before and found it very easy to use so I'd like to stick to it. cheers

This review is for a previous version of the add-on (1.3.2).