[plt-scheme] spgsql "reference to undefined identifier: pg-connect" error

Hi everyone,

I'm a new mzscheme/drscheme user and I'm hoping that this is a trivial 
problem in experienced hands.

I'm trying to use spgsql to connect to PostgreSQL which I have verified 
to be working by accessing it using other language/drivers. I installed 
spgsql by copying it under the collects directory, did "(require (lib 
"spgsql.ss" "spgsql"))" as described in the example (this didn't 
generate any errors), but when I tried to create a connection by 
evaluating (define cx (pg-connect HOST PORT DB USER PWD)) with 
appropriate values for the connection parameters, I got the error 
message "reference to undefined identifier: pg-connect".

Is my installation of spgsql incorrect (calling mzlib libraries such as 
pregexp is totally functional), or the way I loaded the library, or 
something else?

Stephen