Primary Key Problems

Here is a good one. I have three fields set for my primary key. Now I
thought that a primary key was unique, and dups can not be inserted.

CREATE TABLE "inventory" (
"stock" character varying(50) NOT NULL,
"inventory_type" character varying(20) DEFAULT 'unknown' NOT NULL,
"client_id" integer NOT NULL,
[...]
Constraint "inventory_pkey"
Primary Key ("stock", "inventory_type", "client_id")
);

and I insert into the db and get dups.

client_id | stock | inventory_type
-----------+-------+----------------
81 | 2001 | new
81 | 2001 | new
81 | 2003 | new
81 | 2005 | new
81 | 2006 | new
81 | 2006 | new
81 | 2008 | new
81 | 2008 | new

Why did I get dups in my data?

PostgreSQL 7.1.3 on i686-pc-linux-gnu, compiled by GCC 2.95.4

Thanks.

--
Reason: Flat tire on station wagon with tapes. ("Never underestimate the bandwidth of a station wagon full of tapes hurling down the highway" Andrew S. Tanenbaum)
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