Cannot Create Foreign Key

App: pgAdminIII V1.2.0 Post Beta 1 (Sept 17 2004)
DB: PostgreSQL 7.4.2
O/S: Fedora Core 2
Kernel: 2.6.8-1.521

Cannot add a foreign key to a table using the gui provided by the "New
Object" ... "Foreign Key" dialog. The dialog appears complete and I
have filled out all of the requisite parts of the dialog. On the
"Columns" tab, the two related columns are selected, but the "Add"
button remains grayed out.

Regards

Shane Brodie
Winnipeg, Manitoba, Canada

PS: SQL for the 2 tables in case I've lost my marbles and am trying to
do something I shouldn't be, is included below.

CREATE TABLE emp_tb
(
emp_id serial NOT NULL,
familyname varchar(30) NOT NULL,
givennames varchar(30) NOT NULL,
sinnumber varchar(9),
dob date,
photo_path varchar(255),
CONSTRAINT pk_emp_tb PRIMARY KEY (emp_id)
)
WITHOUT OIDS;

CREATE TABLE emp_address_tb
(
emp_id int4 NOT NULL,
address_id serial NOT NULL,
add1 varchar(100) NOT NULL,
add2 varchar(100),
city varchar(50) NOT NULL,
prov_cd char(2) NOT NULL,
postalcd char(6),
CONSTRAINT pk_emp_address PRIMARY KEY (address_id)
)
WITHOUT OIDS;

Relation I'm trying to establish is between emp_tb.emp_id and
emp_address_tb.emp_id ...