Version Discrepancy

pg_config is telling us that we are running version 7.3.6-RH, but when
we start psql it shows that we are running 8.1.4 (which is the correct
version).
  [postgres@mh bin]$ pg_config --version
  PostgreSQL 7.3.6-RH
  [postgres@mh bin]$ which postmaster
  ~/bin/postmaster
  [postgres@mh bin]$ psql imp
  Welcome to psql 8.1.4, the PostgreSQL interactive terminal.

This isn't causing any problems, but does seem a bit unusual. We
purchased a Dell server with RHEL preinstalled, minus postgres, which we
installed ourselves. No non-8.1.4 versions of pg_ctl or postmaster exist
on the server. Any ideas on what's causing this?

Thanks,

Ron