Rated 3 out of 5 stars

Well

This feature is very usefull, then I tryed this steps

1-Install version 3.0 that you can download in http://ftp.mozilla.org/pub/mozilla.org/thunderbird/releases/
2- import your filters
3- check all your filters
4-make a upgrade to latest version as you can download on http://ftp.mozilla.org/pub/mozilla.org/thunderbird/releases/

good luck

Alexandre