dyld error with do_postgres

[biot023]

Hi -- I'm brand new to DataMapper, having decided to use it on a new
Sinatra app (which I'm also new to).
I've done everything right so far (I think), but am getting the
following error when I try to run my cuke features:

dyld: lazy symbol binding failed: Symbol not found: _PQsetdbLogin
Referenced from: /Users/douglivesey/.rvm/gems/ruby/1.9.1/gems/
do_postgres-0.10.0/lib/do_postgres_ext.bundle
Expected in: flat namespace

dyld: Symbol not found: _PQsetdbLogin
Referenced from: /Users/douglivesey/.rvm/gems/ruby/1.9.1/gems/
do_postgres-0.10.0/lib/do_postgres_ext.bundle
Expected in: flat namespace


Can anyone advise me on how to fix this?
I've added pg_config to the PATH, and reinstalled do_postgres, but to
no avail.
Oh, and I'm on OSX Snow Leopard.
Cheers for any & all assistance,
Doug.