Any idea why an application would be getting ora-1410 (invalid rowid) on
the trigger below?

CREATE OR REPLACE TRIGGER t_tbl1
after delete on tbl1
referencing old AS oldRow
for each row
begin
delete from tbl2
where tbl2.media_id=ldRow.media_id
and tbl2.PARTNER_ID is not null;
end t_tbl1;

There are no triggers on tbl2. The application makes no use of "where
current of" cursors, nor does it ever directly reference a rowid.