We have been having problems with Thunderbird on Etch crashing when printing.

Here seems to be a link to the problem:

http://www.mail-archive.com/debian-bugs-dist@lists.debian.org/msg239921.html

By upgrading thunderbird to Sid/Unstable the problem was fixed.

Assuming that you have sid in your sources and that your preferences allow you to override the prefered release, you can upgrade like this:

apt-get install -t sid thunderbird

My preferences did not permit me to upgrade, like that so I just moved them out, did the upgrade and put them back.

mv /etc/apt/preferences /tmp
apt-get install -t sid thunderbird
mv /tmp/preferences /etc/apt/