postgres catalog files problem

Hi,
I noticed that I have too many records in my pg_ catalog files with the same
name. For example
if I give this query, which checks for the triggers that do not have
corresponding tables in the pg_class

select * from pg_trigger where tgrelid not in (select relfilenode from
pg_class),

I get set of records like this (omitted some fields)

tgrelid tgname tgfoid
tgtype tgconstrname
629324 RI_ConstraintTrigger_654082 1644 5
payment_fk_id ...

629324 RI_ConstraintTrigger_654083 1645 17
payment_fk_id ...
........

That is there are records in my pg_trigger that has no corresponding tgrelid
in pg_class. Why is that? Is it okay to manually delete these records from
the catalog files?

So Im getting this errorthis error when I try to update some tables
' could not open relation with oid'

Thanks for your help
josh