Can't run current PostgreSQL

I am trying to run the latest version (supping source daily) and I get the
following error when I run psql.

Connection to database 'darcy' failed.
connectDB() failed: Is the postmaster running and accepting connections at 'UNIX Socket' on port '5432'?

Have I missed some change that I have to make?  This is on the same
system as the server.

TIA.

-- 
D'Arcy J.M. Cain <darcy@{druid|vex}.net>   |  Democracy is three wolves
http://www.druid.net/darcy/                |  and a sheep voting on
+1 416 424 2871     (DoD#0082)    (eNTP)   |  what's for dinner.