Logging not working

Hi. PG 9.0.5, on CentOS 5 with 64 bit.

Here's the logging related items from my config file:

log_directory                   = 'pg_log'
log_filename                    = 'pglog.postgresql-%Y-%m-%d_%H%M%S.log'
log_rotation_age                = 1d
log_min_duration_statement    = 5000       # In milliseconds

That's it.

The directory "/var/lib/pgsql/data/pg_log" is chowned by
postgres:postgres. And it's even chmodded 777, just to be sure that
anyone can write to it. (For now)

Why's there no log then? What can I do?

Thanks!