Stray autovacuum daemon

Hello list

I have a largish postgresql (8.3) instance with autovacuum turned on. I am
doing some heavy importing and I want to vacuum the relevant tables manually
since autovacuum seems to trigger the vacuum in the middle of the import
process which slows things down.

Now, the problem is that I cannot turn autovacuum off! I have tried to set
autovacuum = off at postgresql.conf with no avail. I have also tried to
disable the vacuum by inserting rows to pg_autovacuum but still the vacuum
processes just pop up. What's even more weird is that autovacuum is
vacuuming the same tables over and over. No sign of xid wraparound issues
show in the logs. How can I stop autovacuum without restarting the database
instance?

Relevant non-default configuration values:

autovacuum = off
log_autovacuum_min_duration = 0
autovacuum_naptime = 1min
autovacuum_vacuum_threshold = 500
autovacuum_analyze_threshold = 500

vacuum_cost_delay = 5

Logs:

2008-02-22 12:59:34 EET [23258]: [2-1] LOG: automatic vacuum of table
"xxx": index scans: 0
pages: 0 removed, 15150 remain
tuples: 0 removed, 2123107 remain
system usage: CPU 0.01s/0.00u sec elapsed 151.48 sec

Regards

Mikko