Slow - grindingly slow - query

Hi

I have a single table with two views. The table effectively contains both
master and detail info (legacy stuff I'm afraid). The query in question is
used to see if any records exist in the detail that do not exist in the
master. The table and index definition is as follows

  create table accounts (
    domain text,
    registrationtype char
    /* Plus a couple of other irrelevant fields */
  );

  create index domain_idx on accounts (domain);
  create index domain_type_idx on accounts (domain, registrationtype);

The views are

  create view accountmaster as SELECT * from accounts where registrationtype =
'N';
  create view accountdetail as SELECT * from accounts where registrationtype <>
'N';

The query is

  select accountdetail.domain from accountdetail where
    accountdetail.domain not in
      (select accountmaster.domain from accountmaster);

I started the query about 5 hours ago and it is still running. I did the same
on Informix Online 7 and it took less than two minutes...

My system details are
  postgres: 6.5.3
  O/S: RH6.0 Kernel 2.2.5-15smp

Explain shows the following

  explain select accountdetail.domain from accountdetail where
    accountdetail.domain not in
      (select accountmaster.domain from accountmaster) limit 10;
  NOTICE:  QUERY PLAN:

  Seq Scan on accounts  (cost=3667.89 rows=34958 width=12)
    SubPlan
      ->  Seq Scan on accounts  (cost=3667.89 rows=33373 width=12)

  EXPLAIN

The number of records in the two views are

  psql -c "select count(*) from accountmaster" coza;
  count
  -----
  45527
  (1 row)

  psql -c "select count(*) from accountdetail" coza;
  count
  -----
  22803

I know of exactly one record (I put it there myself) that satisfies the
selection criteria.

Any ideas would be appreciated

--------
Regards
Theo

PS We have it running live at http://co.za (commercial domains in South Africa).