Postgres 6.4.2 connection problem

REGARDING                Postgres 6.4.2 connection problem
We configured an external drive with postgres 6.4.2 such that we could
run postgres/connect via psql, etc.

Upon connecting the external drive to a different machine (same OS, Sun
Solaris 2.5.1 and configuration/architecture), we changed the appropriate
environment variables and updated the pg_hba.conf file with a new host
entry with the IP of the machine.  The postmaster process starts up on the new
machine however we are receiving the following error upon trying to
connect to it via psql:

Connection to DB Template1 failed
Connect DB(): getprotobyname failed

Any idea what causes this error message?

Thanks,
Andy