lots of puzzling log messages

I am Seeing twelve of these messages every five to ten seconds in the
Postgresql serverlog when my java application is running:


2005-04-19 16:43:03 LOG:  00000: duration: 0.246 ms
LOCATION:  exec_simple_query, postgres.c:960
2005-04-19 16:43:03 LOG:  00000: statement: rollback; begin;
LOCATION:  pg_parse_query, postgres.c:464


postgresql.conf has:

log_connections = true
log_duration = true
log_statement = true
log_timestamp = true

Running  postgres 7.4.2.

The Java application uses postgresql-7.4.1.jar. It is a custom developed
application.

I am wondering what these log messages mean. Any ideas?

Dennis