It could be the font thing. Thunderbird has been crashy for me in the past when I screwed up installing fontconfig. Also, it can sometimes be crashy if you get an email with an attachment that has a mime type with no application to handle it in Gnome. I tried to give up Open Office so I didn't install it for a while, then I got some emails with powerpoint attachments which made Thunderbird crash. So I caved and installed Open Office.
It could be something else fubar in your profile. Try re-naming the hidden folder .thunderbird in your home folder (delete a letter, add a letter, whatever) then start Thunderbird and enter all you details again. Hopefully a clean profile will solve the problem. You'll still have your old mail in the renamed folder.