With the latest pkgsrc on NetBSD/i386 3.99.3 (with XFree86 4.4.0).

===> Registering installation for thunderbird-1.0.2
pkg_create: can't stat `/usr/pkg/lib/thunderbird/components/libwidget_gtk.so'
pkg_create: can't stat `/usr/pkg/lib/thunderbird/libgtksuperwin.so'
pkg_create: can't stat `/usr/pkg/include/thunderbird/widget/gdksuperwin.h'
pkg_create: can't stat `/usr/pkg/include/thunderbird/widget/gtkmozarea.h'
pkg_create: can't stat `/usr/pkg/include/thunderbird/widget/gtkmozbox.h'
thunderbird-1.0.2 requires installed package Xft2-2.1.6nb1
thunderbird-1.0.2 requires installed package freetype2-2.1.9nb1
thunderbird-1.0.2 requires installed package gtk2+-2.6.4nb1
thunderbird-1.0.2 requires installed package jpeg-6bnb3
thunderbird-1.0.2 requires installed package libIDL-0.8.5
thunderbird-1.0.2 requires installed package png-1.2.8
===> Cleaning for thunderbird-1.0.2
ROOT n40:/usr/pkgsrc/mail/thunderbird>