Comment 6 for bug 211002

I have noticed the same problem. It also exists with debuild (while signing .dsc file)
I've installed pinentry-gtk2 package and it asks for password now, so enigmail is working.
I don't remember i've installed pinentry in gutsy, but enigmail was asking for a passphrase to decrypt a message. Also I don't remember I've deleted it while updating to hardy and it isn't shown in /var/log/dist-upgrade/*

Anyways, gnupg-agent only suggests installing pinentry, but doesn't require it.