BUG #6535: LEFT JOIN on large table is altering data

The following bug has been logged on the website:

Bug reference: 6535
Logged by: Aren Cambre
Email address: aren(at)arencambre(dot)com
PostgreSQL version: 9.1.3
Operating system: Windows 7 x64
Description:

(Note that this issue is described fully at
http://stackoverflow.com/questions/9713537/postgres-left-join-is-creating-new-data.
A few knowledgeable people have weighed in, and there is no solution
identified.)

In a nutshell, I have a query LEFT JOINing table A with table B and
inserting the data into table A'. A' is a functional equivalent of table A.
Table B is actually built from a using a WITH at the top. I'm using it to
help add a rank() to the table.

Table A has just over 2 million rows.

There is a column named citation_id that has no null values. Not only does
citation_id have a NOT NULL constraint, I have verified with a query that it
has no null values.

The LEFT JOIN is pulling table A's citation_id. However, when the joined
table is inserted into table A', Postgres throws "null value in column
"citation_id" violates not-null constraint" errors.

Note that I am running Postgres 32 bit for PostGIS compatibility.