Forum .LRN Q&A: Response to Message View in Forums is very slow on Postgresql

Here is the query plan:

NOTICE:  QUERY PLAN:

Index Scan using forums_messages_pk on forums_messages  (cost=0.00..3.92 rows=1 width=108)
  SubPlan
    ->  Seq Scan on forums_messages fm2  (cost=0.00..2141.01 rows=1 width=12)

EXPLAIN

I also tried explain verbose, but it have way too much information I think. Here is the table description. It looks like the tree_sortkey has an index.

openacs.org-dev=# d forums_messages
                        Table "forums_messages"
     Attribute     |           Type           |        Modifier        
-------------------+--------------------------+------------------------
 message_id        | integer                  | not null
 forum_id          | integer                  | 
 subject           | character varying(200)   | 
 content           | text                     | 
 html_p            | character(1)             | not null default 'f'
 user_id           | integer                  | not null
 posting_date      | timestamptz | not null default now()
 state             | character varying(100)   | 
 parent_id         | integer                  | 
 open_p            | character(1)             | not null default 't'
 tree_sortkey      | bit varying              | 
 max_child_sortkey | bit varying              | 
Indices: forums_mess_sk_forum_un,
         forums_messages_pk
Constraints: ((open_p = 't'::bpchar) OR (open_p = 'f'::bpchar))
             (((state = 'pending'::"varchar") OR (state = 'approved'::"varchar")) OR (state = 'rejected'::"varchar"))
             ((html_p = 't'::bpchar) OR (html_p = 'f'::bpchar))