For whatever the reason, unace-2.5-r3 reliably segfaults before doing anything (or at least I hope it didn't manage to do a thing). One of the patches in revision 8 of debian patch tarball (either updated or new one) fixes this problem.
http://gitweb.gentoo.org/repo/gentoo.git/commit/?id=43921b2c10cb4dacdcc22c9d2ce2a604e58bac85