Autovacuum not running in 8.2.0

Hi, I recently upgraded from 8.1.4 to 8.2.0, everything was fine
except that I suspect that the autovacuum was not running. In
pgAdmin's server properties, the "Autovacuum" property shows
"runnning", but I couldn't find any log entry for the autovacuum
process. I've set the new postgresql.conf to match the old one (from
the 8.1.4 install), especially the autovacuum entries, but still I
couldn't find any log entry for the process (The logging works fine, I
tried to supply a wrong login password, and the login failure was
successfully logged). Has anyone experienced similar issue?

Regards,

Ming