9.4 on Ubuntu 15.04: ENETUNREACH error?

I recently upgraded to Ubuntu 15.04 with PostgreSQL 9.4.4 with uuids and
plv8 coffeescript extensions. I can access the database via psql. My web
application uses node.js via pg-bricks. It works perfectly on my Mac dev
machine.

On the server, I get this error:

preload failed { [Error: connect ENETUNREACH 127.0.0.0:5432 - Local
(0.0.0.0:0)]
   code: 'ENETUNREACH',
   errno: 'ENETUNREACH',
   syscall: 'connect',
   address: '127.0.0.0',
   port: 5432 }

(Preload is a script in my app that does multiple queries via pg-bricks.)

I have turned off ufw, set pg_hba.conf to TRUST, done everything I can
think of -- no  joy.

Any ideas why this might be happening?

--
νz