question about log entry from trigger execution

I have a database I inherited with a number of triggers defined on various tables.

One AFTER trigger, when executed, causes a database log entry with a “CONTEXT” entry, but no ERROR.  I normally only see the CONTEXT entries when an ERROR occurs. 

The trigger is on table rbs, and it returns NULL.

Here are the entries (slightly edited):

May  5 16:08:21 postgres[18723]: [598-1] 2010-05-05 16:08:21 UTC LOG:  statement: DELETE FROM rbs WHERE id = 136259855 AND cid = 601

May  5 16:08:21 postgres[18723]: [599-3] 2010-05-05 16:08:21 UTC CONTEXT:  SQL statement "UPDATE uinfo UI SET id_bitmap = (id_bitmap & ~(1::bit(128) << (C.bitmap_index

May  5 16:08:21 postgres[18723]: [599-4]  - 1)) ) FROM cinfo C WHERE UI.id =  $1  AND  $2  = C.cid"

May  5 16:08:21 postgres[18723]: [599-5] ^IPL/pgSQL function "rbs__adel" line 6 at SQL statement

May  5 16:08:21 postgres[18723]: [600-1] 2010-05-05 16:08:21 UTCLOG:  statement: COMMIT

The statement that seems to be logged is:

    UPDATE uinfo UI

      SET id_bitmap = (id_bitmap & ~(1::bit(128) << (C.bitmap_index - 1)) )

    FROM cinfo C

      WHERE UI.id = OLD.id AND OLD.cid = C.cid;

The update seems to get done ok.  I still wonder what the log entry is trying to tell me. 

This is PostgreSQL 8.3.

Any ideas?

Susan