Strange query problem...

Um. How is this possible? Am I doing something very, very stupid, here?

mydb=# select * from time_recs where id_time_rec not in (select id_time_rec
from punch_time_recs);
id_time_rec | id_user | record_date | id_code_task | id_code_pay_type |
id_project | time_amount | comment | commit_state | id_domain |
id_code_bill_type | id_group
-------------+---------+-------------+--------------+------------------+----
--------+-------------+---------+--------------+-----------+----------------
---+----------
(0 rows)

mydb=# select count(*) from time_recs;
count
-------
73725
(1 row)

mydb=# select count(*) from punch_time_recs;
count
-------
5369
(1 row)

There are many occurences where this is true...Roughly 68,356, if my math is
right. :)

Table definitions:
mydb=# \d time_recs
Table "public.time_recs"
Column | Type | Modifiers
-------------------+------------------------+-------------------------------
id_time_rec | character varying(38) | not null
id_user | character varying(38) | not null
record_date | character varying(38) | not null
id_code_task | character varying(38) | not null
id_code_pay_type | character varying(38) | not null
id_project | character varying(38) | not null
time_amount | double precision | not null
comment | character varying(252) | default ''::character varying
commit_state | integer | not null
id_domain | character varying(38) | not null
id_code_bill_type | character varying(38) | not null
id_group | character varying(38) | not null
Indexes:
"cpk_123" PRIMARY KEY, btree (id_time_rec)
"ix123_10" btree (id_code_bill_type)
"ix123_2" btree (record_date)
"ix123_3" btree (id_code_task)
"ix123_4" btree (id_code_pay_type)
"ix123_5" btree (id_project)
"ixc123_1_2" btree (id_user, record_date)
Foreign-key constraints:
"f123_10_112" FOREIGN KEY (id_code_bill_type) REFERENCES
codes_bill_types(id_code)
"f123_1_104" FOREIGN KEY (id_user) REFERENCES users(id_user)
"f123_3_109" FOREIGN KEY (id_code_task) REFERENCES codes_tasks(id_code)
"f123_4_111" FOREIGN KEY (id_code_pay_type) REFERENCES
codes_pay_types(id_code)
"f123_5_108" FOREIGN KEY (id_project) REFERENCES projects(id_project)
"f123_9_103" FOREIGN KEY (id_domain) REFERENCES domains(id_domain)

mydb=# \d punch_time_recs
Table "public.punch_time_recs"
Column | Type | Modifiers
-------------------+------------------------+-------------------------------
id_punch | character varying(38) | not null
id_user | character varying(38) | not null
record_date | character varying(38) | not null
id_code_task | character varying(38) | not null
id_code_pay_type | character varying(38) | not null
id_project | character varying(38) | not null
punch_datetime | double precision | not null
comment | character varying(252) | default ''::character varying
id_time_rec | character varying(38) |
when_exported | double precision |
id_code_bill_type | character varying(38) | not null
pre_or_post | double precision |
id_group | character varying(38) | not null
Indexes:
"cpk_173" PRIMARY KEY, btree (id_punch)
"ix173_10" btree (id_code_bill_type)
"ix173_3" btree (id_code_task)
"ix173_4" btree (id_code_pay_type)
"ix173_5" btree (id_project)
"ix173_6" btree (punch_datetime)
"ix173_8" btree (id_time_rec)
"ixc173_1_2" btree (id_user, record_date)
Foreign-key constraints:
"f173_10_112" FOREIGN KEY (id_code_bill_type) REFERENCES
codes_bill_types(id_code)
"f173_1_104" FOREIGN KEY (id_user) REFERENCES users(id_user)
"f173_3_109" FOREIGN KEY (id_code_task) REFERENCES codes_tasks(id_code)
"f173_4_111" FOREIGN KEY (id_code_pay_type) REFERENCES
codes_pay_types(id_code)
"f173_5_108" FOREIGN KEY (id_project) REFERENCES projects(id_project)
"f173_8_123" FOREIGN KEY (id_time_rec) REFERENCES time_recs(id_time_rec)
ON DELETE CASCADE