Rated 4 out of 5 stars

per RTaxi el des. 27, 2009 · enllaç permanent

It's right this add on wasn't updated, i found the solution at this page
http://kb.mozillazine.org/Thunderbird_3.0_-_New_Features_and_Changes.
You can find a link at this web page to the updated version of the add on, it worked for me !!