Works for me on Firefox 3.6.* Rated 5 out of 5 stars

You can get the working 1.1.9 version for Firefox 3.6.* here:
http://tadd.free.fr/temp/stayOnline/firefox-addons/tab_url_copier-1.1.9-fx.xpi

This was done thanks to "Untitled n° 4" 's suggestion!