freaky results

Running postgres-7.0.3 on a RedHat 6.2 system:

Recently I updated the schema of one of our tables (create, insert
select, drop, rename). We have a boolean column "hitsingle" with a default
of 'f'.

media=> \d incantaaudioclipregistry
Table "incantaaudioclipregistry"
Attribute | Type | Modifier
----------------+--------------+----------------------
...
releasedate | integer | not null
...
hitsingle | boolean | not null default 'f'
...

Lately newly inserted rows have been coming up with a value of 't', even
though that column is not mentioned in the insert (and therefore should get
the default value).

media=> select releasedate, hitsingle, count(*) from incantaaudioclipregistry group by releasedate, hitsingle;

releasedate | hitsingle | count
-------------+-----------+-------
...
1237 | f | 1984
1237 | t | 31
1237 | t | 429
1239 | f | 264
1239 | t | 26
1239 | t | 669
...

WTF is that?!

media=> select count(*) from incantaaudioclipregistry where hitsingle and not hitsingle = 't';
count
-------
1098
(1 row)

So, I have T and no T!

I tried replicating the problem on a small scale and couldn't. I can't
even replicate it in the database with problems. Sigh.

I have made copies of the files in base/media/ just in case somebody out
there could perform a forensic analysis.