Problem with function and trigger...

I have a function declared as such:

CREATE OR REPLACE FUNCTION thread_sync() RETURNS trigger AS $$
BEGIN IF TG_OP = 'DELETE' AND OLD.deleted = FALSE THEN   UPDATE member SET total_threads=total_threads-1 WHERE
id=OLD.member_id;  RETURN OLD; ELSEIF TG_OP = 'INSERT' THEN   UPDATE member SET total_threads=total_threads+1 WHERE
id=NEW.member_id;  RETURN NEW; ELSEIF TG_OP = 'UPDATE' AND NEW.deleted = TRUE THEN   UPDATE member SET
total_threads=total_threads-1WHERE id=NEW.member_id;   RETURN NEW; ELSEIF TG_OP = 'UPDATE' AND NEW.deleted = FALSE THEN
 UPDATE member SET total_threads=total_threads+1 WHERE id=NEW.member_id;   RETURN NEW; END IF; RETURN NULL; 
END;
$$ LANGUAGE plpgsql;

And the trigger for it:

CREATE TRIGGER thread_sync AFTER INSERT OR DELETE OR UPDATE ON thread
FOR EACH ROW EXECUTE PROCEDURE thread_sync();

creating the function works fine, as well as creating the trigger, but
when I go to insert a row, I get the following message:

bcodev=> insert into thread
(member_id,subject,category_id,last_member_id) values (1,'hi there
this is a test',1,1);
ERROR:  record "old" is not assigned yet
DETAIL:  The tuple structure of a not-yet-assigned record is indeterminate.
CONTEXT:  PL/pgSQL function "thread_sync" line 2 at if

What am I failing to understand with this?