Adding my "Me too!" here.Since I rebuild thunderbird from Ubuntu, it always used ~/.thunderbird folder. So, after this second debian-based package it breaks with the dialog about "An existing profile.."
Creating a symlink to ~/.icedove shows the same message. But removing the "\ #" comments fixes it.
-- Adilson dos Santos Dantas http://www.adilson.net.br http://twitter.com/adilsond