Just won't install Rated 1 out of 5 stars

I used to love ToneQuilla but try as I might it just won't install any more - either from file [tonequilla-1.1.0-sm+tb.xpi] or directly. OS10.6.5 and now 10.7.2 on a new Mac. Thunderbird version is now 5.0.

The install always "appears" to work and it appears in my add-ons list. Then reboot Thunderbird to activate it and it's vanished. Every time.

This review is for a previous version of the add-on (1.1.0).  This user has a previous review of this add-on.