Can't install /usr/ports/packages/i386/all/libpqxx-2.5.3p0.tgz: lib not found pq.4.2
Even by looking in the dependency tree:
        postgresql-client-8.1.4
Maybe it's in a dependent package, but not tagged with @lib ?
(check with pkg_info -K -L)
If you are still running 3.6 packages, update them.