pg_relcheck

I created a field and then decided to drop it. Postgres won't let me drop it, however. I get the following error
messagewhen trying to drop it using phppgadmin: 

Error - /home/httpd/htdocs/pgadmin/lib.inc.php -- Line: 718

PostgreSQL said: ERROR: Relation "pg_relcheck" does not exist
Your query:

SELECT
rcname as index_name,
rcsrc
FROM
pg_relcheck,
pg_class bc
WHERE
rcrelid = bc.oid
and bc.relname = 'client'
and not exists
(select * from pg_relcheck as c, pg_inherits as i
where i.inhrelid = pg_relcheck.rcrelid
and c.rcname = pg_relcheck.rcname
and c.rcsrc = pg_relcheck.rcsrc
and c.rcrelid = i.inhparent)

Could someone please explain why I am getting this error message.

--
Thanks,

Mark