Comment 3 for bug 886589

I was getting this too, and I think it started when I upgraded thunderbird to 7.0.1+build1+nobinonly-0ubuntu1.

I opened the enigmail preferences and manually set the GnuPG program to be /usr/bin/gpg, but the error kept coming. So I removed the enigmail package from ubuntu altogether and instead installed enigmail from addons.mozilla.org, and everything is working fine now.