Odd 'except' and 'default' interaction behavior

We noticed a strange behavior involving 'except' and 'default'
interaction.  Example from psql:

wpbb=# \d robtest
          Table "robtest"
 Attribute |  Type   |  Modifier
-----------+---------+-------------
 id        | integer | default '1'
 userid    | integer |
 articleid | integer |

wpbb=# insert into robtest (userid,articleid) select '1'::int4,'2'::int4 except select '2'::int4,'5'::int4;
ERROR:  Each UNION | EXCEPT | INTERSECT query must have the same number of columns.

wpbb=# alter table robtest alter column id drop default;
ALTER

wpbb=# insert into robtest (userid,articleid) select '1'::int4,'2'::int4 except select '2'::int4,'5'::int4;
INSERT 306530 1


Notice that error regarding the usage of except and the # of columns.
Strange.  Yet, that exact same query works fine when we remove a
default on a column on the table which isn't being referenced.

I'm not sure if this is a bug, a poorly written error message, or my
ignorance. :')  We are using Postgresql 7.0.3 release under Linux:

phil=# select version();
                            version
----------------------------------------------------------------
 PostgreSQL 7.0.3 on i686-pc-linux-gnu, compiled by gcc 2.7.2.3 (1 row)


Thanks!!


Phil

--
Philip Edelbrock -- IS Manager -- Edge Design, Corvallis, OR
   phil@netroedge.com -- http://www.netroedge.com/~phil
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